Please don't laugh: Holloway House® Quick Shine® Multi-Surface Floor Finish. Easy to use, easy to clean.

For flat and semi-golss, I use Vallejo, but I cannot make their gloss work at all. You may want to try various brands to find one that works well for you.

Clear coats are difficult because you can't really see them. Having a strong light source striking the surface at an angle allows you to see the coating from the glare.