Anyone painted with krylon?

[spyder]

Yes, any spray can will chip but like any paint job whether it be spray paint, professional automotive paint or even latex house paint for that matter, its all in the prep.

A properly cleaned and prepped surface will hold your finish much better and longer

Still in the end, it will chip and flake. It is ok for a quick fix, but if you plan on having the gun a while, you owe it to yourself to use at least duracoat or brownells gunkote especially on plastic parts that will bend and flex.

I wont be painting the barrel but being a bullpup the grip and forearm are taking alot more barrel heat than a conventional layout.
As far as Duracoat I would definitely prefer that but I don't have a paint gun and from what I have found it doesn't come in a spray can.
How would you guys recommend I prep the polymer?

For a one time use, you can get a cheap airbrush that will work fine. They have prefilled canisters you can hook up to them also for small jobs, shouldn't run you more than 25 bucks for the whole set up. Granted, it is gona cost more than spray paint but the moment your krylon paint cracks or chips, you will wish you spent the extra money.