It does thin the color. I've found if you have bare glass spots use you favorite thickener and drag some gel putty over the discolored areas or bare glass before spraying. I make that just thick enough to keep from falling off the spreader when held upside down, or the first coat I'll spray on without the duratec until I get coverage.

Another way I've done it is to use 25% Duratec for the first couple coats and then go to 50%. I use the wax with the duratec in the last coat and I've had great results. Don't be afraid of adding a little extra wax, I've never had a problem doing it this way. I've been told you don't have to use wax with duratec but my experience says use the wax.

PVA is fine for small repairs but you don't need to deal with that if your doing larger areas.

Duratec makes a thinner. It's not cheap but it works great. I've never used lacquer thinner with gelcoat and I wouldn't myself. I've used styrene or patch booster to thin also with fine results.

Just my .02.