I successfully applied the base coat to my A4. I used Ultrabrush applicators dipped directly into the OEM paint pen (after removing the entire cap assembly). The base color flowed nicely leaving a smooth, even surface.

My prior experience with the top clear coat, however, is that it is thick and does not flow into the area that I'm trying to fill. I used the same type product that came with my VW touch up paint.

What can I use to thin the paint?