I've been playing with Krylon & Krylon Fusion Primer and the results are OK but the durability just isn't there w/o some clear coat over it (even then it's still not up to par as a solid plastic).
If you don't shoot your rifle Krylon can look great, but I consider Krylon more for a field expediant method of camoflauging with the intention of periodically touching it up. If you're concerned about the Armalite pistol grip matching the Cav-Arms Stock then I don't think Krylon is the way for you.
I'd be taking a look at some of those fancy epoxy type paints that require oven time for something that will look good and take a little abuse as the guys above are recomending.
Edited to Add:I remembered a neat job BRASSPILE did. He had a thread on it (what he used - how he did it) in the Team Section earlier this year. You might want to contact him about what type of paint he used. Here is the result:
It stuck in my head because I want to do a pink furnature AR for my daughter - but Cav Arms doesn't make a Pink A1 or A2 grip and the Ergo is a bit big for her hands. That and I'd rather use the M4 style stock with it's larger buttplate than the smaller CAR stock (they only made the CAR telestocks in Pink).