One thing to keep in mind is that CA doesn’t penalize missed shots and rewards speed; it’s more important to shoot quickly than to make sure each shot is a crit. Sheer volume will increase your CA count faster and maintain your stack better than going for a perfect shot every single time. And as you practice, you’ll naturally get more crits than not.
When I’m using CA, I generally fire from the hip 99% of the time, scoping is too slow if you’re trying to increase/maintain a stack while working through a map. Also try to pull off at least 2~3 shots at a time, with the expectation that at least 2 of them will be crits. That requires some comfort/familiarity with how the recoil of your gun works–again, practice will help with that.
Distance…I guess mid-range, but that’s kind of vague. You know that nomad that pops up across from you in the first room of the Bloodshot stronghold? for me, that’s the closest I want to be to an enemy. Farthest would be just outside the effective range of enemy SMGs, ideally with some cover nearby in case some dick spawns with a vladof sniper. IMO that’s the ideal range for quickly aiming w/o scoping.
As for Deception, I like to engage mobs first, then throw out the decoy when they close in to regain space. Pretty simple.
I mostly use dahl and vladof snipers for their stability and speed, respectively, when hip-firing.