The poisons in the book - anesthetic, neurotoxin, and paralytic - require a Resilience check against a fixed difficulty from the one exposed to them. They can be administered with an aerosol/spray. If such a use in combat is planned, does it require a skill (Medicine?) check on the part of the one spraying the poison and is spraying poison an Action (I assume so)? How would the results of this skill (Medicine?) check alter the target's Resilience check?

I suspect ranged light makes more sense. Kinda like using pepper spray, though I'd probably make it range engaged and use the melee difficulty...

I dunno.. Tricky one

I would let the PC (or GM if an NPC) choose the skill he wished to use. A Coordination/Athletics check might make sense here, and the target only has to do a Resilience check if the attack succeeds. Multiple successes or advantage/triumph might make more setback dice or upgrade the dice pool on the Resilience check.

I have my medic using Medicine, with agility or brawn some times, or a straight up Brawl attack, using her injectors with knockout drugs. Hers are stronger too, home made stuff

I usually just apply the anaesthetic's strain damage if the fail - although she's not always happy about that simple solution. Arguably you could add either successes or advantages as extra strain damage if they fail the check, or as base strain damage that needs to penetrate soak, before the injector affects them. Of course, this is a different approach than the spray-on-knockout you're talking about. I have to remember not to inform her of that solution

I'd say Ranged (light). While I understand the Medicine argument, I think it's still about a ranged attack. I'd only apply extra strain or damage per 2 successes and/or advantages though as it's a different type of weapon, and only if they fail the check, or you could increase/upgrade/add setback dice to the Resilience check based on the attack roll with the spray-on-sleep/poison.

I've still to come up with a satisfactory solution that is 1) not too powerful and 2) does not discourage the player from that using strategy - the second because it's how she tried to solve conflicts early on, yeah I know, and still prefers to. Even if she is getting fond of her Disruptor rifle...

I had a pacifist medic character who used anesthetics and paralytics to avoid harming people yet still ending combat and protecting others. My GM let me use a medic check while using an injector.

It would also make sense that the characters could get a hold of something like a tranquilizer or dart gun to do injections from a distance. That would pretty much be a straight ranged light or heavy attack depending on the type of weapon.

I'll add that Enter the Unknown has burning gel - a spray of acid used to burn through things - and using it in combat is noted as not requiring a skill check, so it could be that poisons are the same.

For a spray on tan... Erm, poison that could work also. In some situations, not that combaty, skulduggery or deception could work also.

It all depends how player describes how his character is gonna use it.