Yes. This.

Do you as a GM require a check when putting the disguise on? Would this be skulduggery? And deception when trying to act correctly with the disguise?

Is it a "passive" check, setting a difficulty for NPC perception checks?

How does the kit actually enter into the check in your games? Boost die if you require a check when putting on the disguise? A setback or upgrade for NPC checks?

I require a Skulduggery check. If the intent is just to disguise themselves (not look like themselves) the check is simple, and I use the results as the opposition to an NPC Perception (successes become difficulty, threats become boost, etc.). If the PC was very noticeable for some reason I would likely have a difficulty.

If the intent is to look like something specific (like a customs agent) then I'll assign a difficulty to the check that seems appropriate and apply results the same way.

I give a boost die for having the disguise kit, and it will reduce the difficulty of the "look like something specific" check.

I play it very situationally.

I also allow the player to make disguises ahead of time, generally more like alternate personalities.

Without a kit I would be increasing difficulty and/or applying setbacks.

I also agree it would be deception to speak/act appropriately if that was necessary.

If the players will go along I like to make the dice roll and keep the results secret. For instance I had a session a while ago where the player was wanted by a particular criminal faction, so he made a general disguise to not look like himself. He had like 3 successes and 2 advantages, but I had applied a difficulty upgrade with a DP, and the roll had a Despair. So I knew that while the disguise was generally very good, that members of the specific criminal faction that he had met before would instantly recognize him through the disguise, but the player had no idea.

Yes and yes and yes.

Making the disguise sets the bar on how hard the perception/vigilance checks of the NPCs are. The complexity, quality, and knowledge of the subject to be disguised as determine the check. Successes, advantages, etc.. above that set the bar for how difficult the disguise is to be seen through.

Actively interacting with others while disguised requires different interaction checks (not always deception) but there's always a risk of the NPCs seeing through the act/disguise.

I typically rule that the disguise kit adds 1 boost die to the skulduggery check (circumstances may vary), since I restrict assistance to being from people with at least 1 rank in the same skill, I think that's fair. 100c for a free assistance.

I was thinking that the characters say they use the kit, state what they do and use (if they've found outfits the are suitable too), and then NPCs roll perception against thenskulduggery of the character that does the disguising (plus a setback die for the kit, and perhaps another one for authentic, in this case, Czerka uniforms - could also be an upgrade).

It seems more ... Plausible.

Alternately, their successes generate the difficulty, but I'm unsure of how to translate that in a plausible manner...

23 minutes ago, Jegergryte said:

I was thinking that the characters say they use the kit, state what they do and use (if they've found outfits the are suitable too), and then NPCs roll perception against thenskulduggery of the character that does the disguising (plus a setback die for the kit, and perhaps another one for authentic, in this case, Czerka uniforms - could also be an upgrade).

It seems more ... Plausible.

Alternately, their successes generate the difficulty, but I'm unsure of how to translate that in a plausible manner...

I think there are definitely at least two ways of looking at it.

1) The disguise itself is static. This is how I play it. The check for success is made when the disguise is created, and remains the same while the disguise is worn. Naturally circumstances can evolve this.

2) The disguise is dynamic. Each time there is an interaction the PCs Skullduggery skill is used to oppose detection. The roll of the dice representing the PCs Skullduggery skill will vary each time, possibly representing all the little things that might give them away.

I can easily see both ways. I use method 1, probably just because that is how I have always done it. Also I feel I think of the disguise as a thing of a certain quality, it could even be purchased, and that Deception is the skill that would represent the little things that might give them away. Both reasonable.

25 minutes ago, Jegergryte said:

I was thinking that the characters say they use the kit, state what they do and use (if they've found outfits the are suitable too), and then NPCs roll perception against thenskulduggery of the character that does the disguising (plus a setback die for the kit, and perhaps another one for authentic, in this case, Czerka uniforms - could also be an upgrade).

It seems more ... Plausible.

Alternately, their successes generate the difficulty, but I'm unsure of how to translate that in a plausible manner...

Minimum difficulty: Simple (you at least got a wash, the costume was assembled but the quality may be less than desired).

1 success or 1 advantage beyond the 1st can add a setback. Then its 2 successes/advantages (beyond the 1st) for an increase in difficulty. 3 success/advantage or Triumph upgrades the difficulty by 1.

And then of course the reverse: 1 failure/threat adds a boost to opponents checks. 2 failure/threat decreases the difficulty (minimum simple, if there, adds a green to their check). 3 failure/threat or 1 triumph upgrades opponents checks by 1.

To me disguise kits are just another sort of tool kit. To use them requires no check at all. It's use is covered by the "Right Tool for the Right Job" benefit.

Disguise kits are generally used in one of two ways: to make yourself less recognizable, or to make yourself appear to be someone else - whether that is a specific person or another species.

In use, the disguise kit gives the disguisee a bonus die to their Deception checks for disguise purposes. If they succeed, the disguise worked; if they fail, the disguise did not.

I ran it as an opposed check, against the PCs Skulduggery (disguise/forgery - looking legit and as someone else) and Deception (pretending to be/acting like someone else in conversations and negotiations).

It may have made things a tad too easy ... but it was exciting for the players whenever I rolled. More so than usual I think.

My PC's used a disguise kit recently. I had them roll Deception for its application, though Skullduggery is good too. The difficulty depended on how crazy they wanted to go with it.

The Bothan dyed his fur that would be visible (hands, face, neck) black.

The Umbaran applied make-up to darken his skin tone to a more human coloration. Wore contact lenses, and dyed his hair black from white.

I generally don't have strangers roll to percieve through the Deception unless they are particularly inquisitive (Guards, Hunters, Law enforcement, etc.) But I do like to make the disguised PC's roll cool checks to see if they can hold their nerve and not act skittish.

17 hours ago, CloudyLemonade92 said:

My PC's used a disguise kit recently. I had them roll Deception for its application, though Skullduggery is good too. The difficulty depended on how crazy they wanted to go with it.

The Bothan dyed his fur that would be visible (hands, face, neck) black.

The Umbaran applied make-up to darken his skin tone to a more human coloration. Wore contact lenses, and dyed his hair black from white.

I generally don't have strangers roll to percieve through the Deception unless they are particularly inquisitive (Guards, Hunters, Law enforcement, etc.) But I do like to make the disguised PC's roll cool checks to see if they can hold their nerve and not act skittish.

Don't make them roll Deception, but great way to spend Threat on social checks that the NPC starts suspecting something and his next check is a Perception against the PCs Deception

9 hours ago, Rimsen said:

Don't make them roll Deception, but great way to spend Threat on social checks that the NPC starts suspecting something and his next check is a Perception against the PCs Deception

That's a good idea!