Okay my two cents

I have been using cage traps because of my Commercial ADC Business for 30+ years. I have used only two methods. First go and have a sheet metal tray made. Make it 1" longer and wider than your largest trap that you want colored. Make the tray say 1-1/2" high.
Now use either paint or speed dip your choice:
(put on disposal latex gloves)"PAINT" ~ If you use paint buy"Red Devil" Polyurethane Oil ENAMEL paint and get a couple of quarts of it.
Pour the paint into the tray and lay your trap into the tray and let it run over all of the metal bars, etc. Flip it around until you have the whole tray covered in paint.
"SPEED DIP"Same process except get away from the gasoline. I use "Mineral Oil." The reason is gas makes the speed dip sticky and the mineral oil does not, plus it has "no smell" period. Follow direction on the speed dip can for how much gas to use and use mineral oil instead. Also you can store the left over in a bucket.
I use this method on all of my trap including my foot-hold and bodygrips.
Let us know how or which one you tried and like.
John
John Consolini CWCP
I might as well use it, I earned it: CWCP ~
Certified Wildlife Control Professional