My molded plug project is still in its infancy and painting in any capacity is not important as form and function. There are some options that I have used and one I haven't explored yet.
All of the needles in the above picture were not painted. Rather in the mold, prior to pouring, you "paint" on a fine aluminum colored dust. All are pearl colors, I haven't looked for anything that is a flat color. It bonds to the plastic as it cures and holds well without an epoxy finish coat. It shows the typical hook rash much like wood plugs. It is the simplest way to go fish and test the plug with color on it before committing to airbrushing/epoxy.
Two other methods I've tried are derivatives of ink. One is to mix a concentrated ink dye into the plastic. The plastic cures opaque white so using more dye is needed to achieve the desired color. I tend to use this if I am making a plug that is dark in color so that the hook rash isn't as pronounced. The second method is supplementing the aluminum dust by using a copic airbrush. It uses ink markers in an airbrush like holders to spray a mist of ink onto the plugs. It dries a bit tacky so I've put it aside as I don't wish to epoxy the plugs.
Airbrush Paint!
It works, but I haven't done it yet. I handed a couple plugs to a friend at the CSA show last month and one of his friends Ryan Hickey offered to paint them. They came out sweet.
