Here's a good technique. I wish i had used this method the last time i marked lowers. Things you will need, Testors model paint and the Testors enamel thinner. Rubbing alcohol Paper towels Card stock or paper board from old packaging or cereal/cracker boxes. You will find that the stuff that has printing on it works best because the printed side is slick and won't absorb paint. More on this below. Tooth picks Masking tape Clean the areas you are going to paint with rubbing alcohol and then wipe dry. Dip a tooth pick in the model paint and start filling the engraving until the paint is just slightly above the surface. Make sure every part of the engraving is filled to the top. If its starting to leak onto the top surface that's when you know its ready. Cut a strip of your card stock about 1/2 inch wide and like 1-2 inches long. Make sure the short side is nice and straight. You are going to use this like a squeegee so you want your edge to stay flat against the receiver. Put the short side against the receiver and lightly drag it across the painted area. If your card stock only has printing on one side make sure the printed side is against the paint. Paint is going to flow all over the surface as you drag across but that's ok. The printed side is slick so its going to smooth out the paint. Drag any big paint drops away from your engraving and clean them up with a paper towel. The goal is to get the paint flat with the surface of the receiver and not have any puddles around the engraving. There is still going to be some surface paint but that gets cleaned up later. Once the paint is even with the surface of the receiver, let it dry for about 15 minutes. Put some enamel thinner on a paper towel and start lightly wiping the surface. Get a flat spot in the paper towel and just drag it across the engraving. You will be able to pull the surface paint away from the engraving then scrub it away. Don't scrub on the engraving or you will pull the paint out. When all the excess paint is cleaned up I will put some masking tape over the area to keep dust out of the engraving as its drying. Let it dry overnight before handling. It takes a few days for the paint to fully cure so don't use any gun cleaners until its cured.