Whatever the manufacturer states roughly.I run slower on my reducer than the stated temp range in PPG.If it's 90 deg and humid I mix it for 100 deg roughly,it has a few advantages.EZ's right,it sounds like you pounded it on.This damn sun will play with you though,I've waited to block and buff and down the road a few months it does change but I'm using uncatalized basecoat.If you already sanded it real good and buffed it go easy this time,you're getting close to the point where you're thinning you clear too much unless you did 3 coats for a 2 coat clear.