When painting the tailgate, first spray over the letters with several good coats of the color desired for the letters. Then spray the entire tailgate with your body color. After the paint has set/cured, carefully sand the body color off the raised letters, leaving the letter color visible. Then clearcoat the entire tailgate if desired. The two colors will somewhat "fade" from one to the other but I think the result looks much better than trying to hand paint the letters.
I remember the custom cab's from the 70's at the dealer and thinking to myself those tailgate letters were put on with a roller. Yes just like license plate.top of the letters look better, like a license plate back when we had embossed plates, BTW I hate the flat plates we now have.
Try using a making fluid. Roller paint the letters & let dry then remove the masking. Works good.
Why not I painted my Az copper 1934 plates that way & they came out just fine & DMV ok'd them. I'd have them on the car but for the fees for classic plates. Besides somebody would just try to rip them off. Copper is in demand ya know.
That is fine if you have a steady hand & a good brush. Thanks but I will use the masking liquidYou can mask all you want, but with raised letters, there's no need to mask.