Hey, I have a second Mossberg 835 Ulti Mag 12 gauge shotgun barrel that my wife did for me in a camoflage pattern. It looks excellent. My part was to first get all of the residue of any oil off the barrel,(good mineral spirtis will do) and then lightly (600 grit) sand the entire barrell even under the vent rib. Take your time it can be done. Now my wifes part. She does air brushing, and first sprayed the entire barrel with exterior primer from a car paint shop. Then I sand again. Until real smooth. Then she mixed her camo colors, and air brush a real nice pattern on it. Looks good and you would swear it came from a factory. Hope this helps. Been using it about a year and a half and it is still perfect. The trick in all good painting is the foundation, it must be real clean, and have a real good primer on it. Hope this helps.
Joe