I use 1cc water in .22 cans mostly. 2 or 3 would probably be the most I'd put in a full size 9mm can. I'm guessing the wire gel to be about the same. Not sure how well it'll work with .45 but it makes a bit difference with .22. To keep that performance up you gotta redo it every mag or so.
I’ve dunked cans in water and shot them, both with 45 and 22. I’m not saying do this, but I would venture and say it’s not critical. You can be a little liberal with it.
I keep it simple - a little water holding it at a slight angle and rotating it so as to distribute it throughout the baffle stack, then give it one quick flick / shake and call it good.
I just pour in a little Ozarka, shake it around, then shake it out and shoot. Remember, anything you put in a pistol can will end up on your glasses, I'd prefer that be water.