So, as i understand (which i don't know if i am right), each model in a unit may choose to throw a grenade, meaning a unit with 6 models could throw out 6 smoke tokens?

I think i will split fire, ie fire all but one trooper at a target and the last throw smoke to cover the unit.

Do I have this right?

Normally, grenades actually add a new weapon profile you can choose to use with various effects for the different grenades.

The smoke grenades instead give you a new action you can use (sorry, cant look up the name now, iirc it's just called smoke, right after the grenades in the rrg) that let's you place a smoke token, they dont add a weapon and this action is not an attack.

45 minutes ago, Thalandar said:

So, as i understand (which i don't know if i am right), each model in a unit may choose to throw a grenade, meaning a unit with 6 models could throw out 6 smoke tokens?

I think i will split fire, ie fire all but one trooper at a target and the last throw smoke to cover the unit.

Do I have this right?

No, as @Steck638 said, the upgrade doesn't give you a weapon like the other grenades, it gives you a card action, and looking at the last version of the RRG, the Smoke X is a unit keyword, meaning that the effect it has is for the whole unit and not for each mini. The "X" indicates how many smoke tokens that unit may place.