[MDPotter]

It's generally not best practice to spray polyester over 2K urethane. Typically polyester is sprayed over epoxy or filler, then you sand it, maybe reapply and sand again depending on how it blocks out and then you apply 2K. 2K doesn't build nearly as thick and is meant for "fine grading". I used a spray polyester once and wasn't a fan - it's like spraying bondo so you have to mix it quick, spray it quick, and clean the gun quick. Much more flexibility with 2K or even epoxy. 2K dries quicker but isn't always recommended over bare steel (depends on the manuf) whereas epoxy can be sprayed over anything but takes longer to dry.

In the end, just read the TDS for the products you're using but I would be leery of polyester over 2K. It's like applying filler over 2K - you're supposed to be done with filler work by the time you get to 2K to do the "fine grading".