Get a heavy piece of cardboard and lay out a grid of holes in it to paint the tips.

Measure how far down the paint goes on the projos, it's about 3/8" down from the tip (eye balling it), don't know how accurate you want it. Then punch a hole in the cardboard to see how big you'll need it to be to go that far down on the projo.

You could line up the rounds in a 10 round straight line or 50 rounds, 5 rows of 10 or 100 using the same lay out. Measure how far apart the center of the tips are from each other, this will make transferring it to the cardboard easy. Mark the centers on the cardboard and then punch out the centers. I would think that you could use a .45 case with the primer punched out to cut the holes easy. With the primer out, it will make it easy to center it, use a hammer to hit the case and cut the hole.

Lay the cardboard over the rounds and spray them from all different angles to get good coverage. If you have a tray that you use for reloading 50 BMG, you can use that to stand them up to make the layout on the cardboard. I use the 12ga. Trays from the Plano hard plastic reloading boxes. The trays hold 50 rounds and you get 2 trays in the case, I use one for reloading and the other to hold the rounds in the case.

ETA: The cases are MTM Case Gard, not made by Plano. You can buy them single or a case of 4, which is the best way to buy them. They will hold a handloaded AMAX round standing upright in the holder. The extra trays can also be trimmed to fit into a 50 BMG ammo can, so very nice to have! I'll have to find the ones that I've already fit into cans and post a pic for you.