I've never used Xtracrylic paints, but I've got, and used, a lot of Xtracolor enamels, mostly on my airliners. I've never sprayed any of them and not had any problems with the coverage.
But, and it's a big but, they need LOTS of mixing to get the density correct, maybe 2-3 times as much as Humbrol enamels, plus they take for ever to dry so I usually give them a brushed coat of Klear, with a wide flat brush, after 5-6 hours and that does the job.
My mixing system isn't just the twirled bit of sprue though, I have a 1965 vintage slot racing motor which has a 4-5" long length of brass tubing soldered over its shaft, which has the last 1/2" bent through 90 deg. and twisted a tad so it looks like a single bladed propeller. Powered by an old model railway controller running at 9-10V and with a makeshift 'switch' on one motor brush it makes an ideal paint mixer, and it's served me well since the 70s.
You may well ask why the paint doesn't splatter itself all over the model room, and me as well, when it's being stirred, but I have a solution for that as well. I use a dead toilet paper inner cardboard roll, chopped into three pieces, and one piece slipped over the opened paint tin so that I grasp the tin THROUGH the roll. Then any splattered paint ends up on the inside of the roll and not over the outside of me.
