If your looking for a product that works over metal, plastic, wood then Duracoat will work great. It comes ready to spray with the addition of hardener (really an activator).
You have several hours you can use in sprayer yet dry to touch in 20 min and ready for assembly in a day but better to give it a few days to really appreciate the hardness and quality of this finish.
The best deals for this finish can be found by calling 800-830-6677 and ask for Steve @ Lauer Custom Weaponry or you can check out their web site at: http://www.lauerweaponry.com
They have been profecting this finish since '94 and rather than ordering just a single color, I like to get there color kits which include 4 or 5 different colors and enough hardener for all. The only other item you will need will be some reduce to keep product spraying smooth.
I like their Woodland Signature Pac for color content. these are matte finishes in this pac with many patterns which can be done with these colors. But they have some other very neat packs as well.
You can get just there Matte Black for just the action and barrel and it gives a very nice flat finish and very sharp appearance when the surface has been sandblasted.
Also if you choose not to do it yourself or wish to do entire rifle try: http://www.ironbrigadearmory.com
they also spray on some really neat patterns.
Hoped this helped,