You wont need a sand blaster to paint anodized aluminum, its perfect the way it is. If the barrel is parkerized then you wont need to blast it either. If you coating platic parts then it may need to be roughed up in a blaster w/ 80-100 grit aluminum oxide first NOT BEAD BLASTED.
fully degrease degrease degrease. and wear latex gloves as the oil from you hands will put oil back on the part being coated
all of this is sound advice no matter what method of refinishing you are choosing.
ease of DIY in order for you to choose from
Camo tape
Krylon
alumahyde
Duracoat
Moly resin
Paying someone else
Cerekote
the rifle redneckmedic posted was duracoat.