OK, I am obviously doing something wrong. I am using Rustoleum Pro thinned about 20% with 100% mineral spirits. I am applying using the roller, which I load up and then roll out on the tray so that I only put on a thin coat. After about 5 minutes when most of the bubbles have gone I drag a dry foam brush across the surface using only its weight as pressure. The surface looks very good, not a mirror but quite close. I leave it about 2 days, clean the surface with the mineral spirits, let them evaporate and repeat again.

Then I do a wet sand. I use 1500 grit to try and remove the faint brush marks that are left as well as any dust that has settled during drying (not much as I'm doing this in the basement). Every time I seem to go through to the previous paint layer in a few places, which then means that I am stuck with those ridges.

Everyone says to do thin coats, but that's no good if I keep having this problem. What am I doing wrong?

Thanks