I got it at home depot in the same place they have the acetone, mineral spirits and such.

A bunch of pages ago, I think someone mentioned using an enamel hardener. Has anyone tried enamel hardener with Rustoleum? I'm thinking the secret recipe could be rustoleum, penetrol to make it flow, and enamel hardener to improve scratch resistance. In my experience it just doesn't get hard enough on its own, even with months of drying.