I too have experimented with rolling on paint, but never thought to thin it as much as suggested. I have found a paint called Rust Scat that is a polyurethane high gloss enamel I had tried with some success. There is also a liquid material that would thin the paint that is called penetrol, it makes the paint flow smoother when using a brush, so I think it would work as a thinner. I am still curious if anyone is trying the Rustoleum from the USA market vs the tremclad, to see how they like it.