I use an old brake cable, pass it from the tire side through a spoke hole, across to the other side and out another spoke hole. then hang it up for paint.
I use an old piece of inner tube with the valve stem still attached. Push it thru the rim, screw on the valve stem cap, and then run a wire hanger thru the cut pieces of inner tube so I can hang it from whatever tree branch is the appropriate height. It does leave a tiny ring around the hole the same diameter of the valve cap but that's easy enough to spot-shoot before the second coat goes on.
I used to do that also but them you have them blowing around if you shoot them with a gun so I wised up and came up with this idea(flake and candy aren't forgiving so they need to stay put when shot!):
2 coat hangers taped together so I can hold it and rotate to make sure it gets even coverage(like I said. Candy paint doesn't forgive!) Then just hang with another coat hanger(the one in the middle that isn't taped) to dry. Bonus is I have a million wire coat hangers from my work clothes so I don't have to spend a dime! :lol:
I use an old inner-tube - looped around the rim exterior and cinched with a pair of grips or simply twisted and duct-taped . The 'extra' gives a loop for the hanger........ obviosuly have the valve facing outwards or at the top out of the way...... holds it good and tight and leaves the whole area clear for painting.