Application temp and humidity

[RP27G8]

The problem is the RustSeal cures two ways, by evaporation of the solvents that are in it (not much), and the resin cures with exposure to ambient humidity. If either or both are too high, it may cure too quickly, leaving brush marks.

If you thin it slightly (5%) that will slow it down as more solvent needs to evaporate out. Your suggestion to apply in the evening or even early morning when the temps are down is a good idea and should help alot.