The best way is to spray it, but you could also roll it-you need to use an oil (or BIN) type primer, nothing water based...that's the whole issue. If it's not primed this is the key, if it is use any paint you want.
Fixing it after it fails is FUN! not....
I think you should definitely check out this thread...
http://www.painttalk.com/showthread.php?t=499&highlight=popcorn