Honestly, you should have replaced the rotors too when the pads were that far gone. Grinding down to the metal usually scores the rotor surface pretty bad. Just doing pads is a cheap fix now, but it might not last.

Ugh, those reps never work with the stuff in the field. Direct sun cuts the working time in half, easy. On hot days, we mix small batches and keep the jug in a cooler with ice packs. Applying in the shade is the right move, even if it's slower. A helper to mix while you trowel can save your butt. We also wet the surface down right before application, it buys you a few extra seconds.

My buddy's kid said the same thing about his old truck. He took him to the junkyard to find a part and the kid's eyes lit up when they got it running. Now that kid wants to learn everything.