No extra effort, but make a stealth check to remove the grate quietly, otherwise, they'll be alerted to your presence and won't be vulnerable to your sneak attack. What you could do if you want is your Ultimate Aim then extra effort to make the attack.Would I need Extra Effort to get the vent cover out of the way and also aim? My plan is to use Ultimate Aim next round and, depending on whether or not these guys are Minions, either Takedown 2 or just do a Multiattack to basically Deadeye them. Or do I need Selective on that?
Selective is not necessary for takedown or multiattack. Takedown 2 lets you attack basically until you miss or rrun out of targets, multiattack is limited to firing across and "arc" which the book does not elaborate on further, but with the gunmen more or less lined up, seems fair enough you could do that too, but remember you take a penalty on the attack equal to the total number of targets, which one the rear entrance is 8 targets, though with a automatic (non critical) 20 on the attack roll itself on possibly vulnerable targets.....you're pretty much guarenteed to hit them all, whereas with Takedown, you could roll a 1 (They are minions, but I am not saying if a routine attack will hit them or not, you gotta take that chance yourselves! So there!)
ALSO! I need initiative rolls for Dusk and Starlight. I'll be putting the initiative order in my signature for easy tracking!