A few things to know about duracoat.
Don't get a cheap airbrush...like any refinishing, quality tools/materials will always yield the best results. If you're on a budget, you can get paasche dual-action brushes on ebay pretty cheap.
Those tiny diaphragm air compressors aren't that great. They'll put out a max of about 40psi (which is fine) but you'll experience some pulsing...especially if you're using less than 10ft of hose. Moisture is another problem.
Also, canned air doesn't work too well. You usually run out before the project is done, the cans freeze over, and they get expensive quick.
If it were me, I'd go buy one of those cheap 3-5gallon "air tanks" sears/craftsman sells. They're inexpensive, and can be filled for 25 cents at your local gas station....each filling will EASILY be enough air to run your airbrush for 1-2 rifles...you'll still want a regulator and filter.
Duracoat requires a perfectly clean surface. Degrease very well (a heated acetone bath works well). Heat will allow the pores in the metal to expand, and will leach out any oil that might otherwise be trapped. Duracoat HATES oil.
Also, duracoat only does "okay" over polished/smooth surfaces. If possible, bead-blast your parts prior to coating.
Ideally, you would parkerize the parts after blasting (but before duracoating). This gives a great surface for duracoat to adhere, and will give your the most durable results.
Parkerizing solution is relatively cheap...but getting a tank long enough to support a barreled action is tough.
I do small parts in a crock-pot (slow cooker) and the others in a home-made 32" aluminum pan.
If you want to save a little money, there are other finishes out there that come in an aerosol can--duracoat even makes one. Most require baking to cure, and from my experiences are a bit more brittle, but they do work quite well. It's less money/headache for setup.
Best of luck.
