Micro Mask Liquid Masking
Micro Mask is like masking tape in a bottle. Just apply it with a brush, let it dry, and cut it to any shape you want with a sharp-pointed knife. Peel out the part where you want to paint, leaving an outer stencil mask, and paint with the method of your choice.
Just don't use a water-based paint over it because Micro Mask is water soluble, so use solvent-based paints. You can paint the finest detail you can cut with a knife. Unlike masking tape that can allow paint to go under it,even the most difficult designs come out sharp and clean with Micro Mask. "