Very easy!
From the time I walk into the shop till finish spraying on a barrel is about 30 minutes.
A $9.95 sandblaster nozzle/siphon hose, $8.99 airbrush, #120 grit aluminum oxide(for steel-220 grit for aluminum), masking tape, disposable gloves and some denatured alcohol for cleanup. I use an electric space heater to pre-warm the parts and a $25.00 used kitchen stove to bake. If you already own an air compressor, figure $100.00 to setup nicely.
The first 10 guns I did with 120 grit sandpaper and the GunKote in spray cans. then sneak 'em in Wifey's oven. Even doing it with sandpaper I have 1 bolt action slug gun that has had the finish for over 25 years.
The spray cans do a good job if you put on really thin coats, the nozzles will,"spit", if you try to spray too fast. The airbrush really speeds up the process.
I'm going to do an 870 receiver this weekend I'll post some pics after.