I didn’t use any thinning at all. The outside temp was 30C, the sun was hammering on the doors and the asfalt. Local temp around me maybe 45C and the tar was as liquid as ordinary paint. The tar disappered into the wood in minutes, leaving a dry surface. Myself, I was sweating like a horse
@Handy_Andy You may actually have a point there. But I think the most important factor is protecting the wood from water.