I picked an Aersal Can from walmart for 4.72 + tax. It acts as a foam. It works pretty good. I dont have any b4 pics of the upper im working on, but Gunscrubber and Brake cleaner didnt phase it. The paint was caked on pretty good and built up (I dunno what some ppl are thinking when they do this shit. lol). I thought it may be hopeless and ive have to resort to scrapping the paint off and tryin to get inbetween the grooves on the upper (this is Flattop). So far this stuff is doin pretty good job. Its messy, ya have to wipe all the crap off but its working, soon ill have a Black upper. I dunno what the over all finish will look like, but ill lube it all up inside and out with CLP.
*EDIT*..I jus found out the hard way. They recommend wearing chemical resistant gloves, I would suggest this, I got some on my hand directly, itll put a hurting on ya. I rinsed hand real well with cold water. it helped. but I was atleast using eyeprotection to spray this stuff on. So dont take chances protect yourself. One lil drop in your eye could mess you up for good.