I used essentially the same process with my 6 month old car, so will add my thoughts.
1. I just gave 1 very thorough wash and then clayed the car. You'll need to wash again after to get the residue of the
clay lube off, then dry again.
2. I went over the entire car with PPP using my
UDM, and buffed it to give a superb finish.
3. I then applied
PGP immediately and left to cure outside for 24 hours - it was warmer then...
4. Next morning I simply wiped over with the QD and soft MF towel to remove any dust etc and then applied another layer. Have repeated that process to have 4 layers on now.
I would apply the PGP in the warm garage and leave to cure. It will actually dry quickly so you are safe to drive it once fully dry. The curing I understand to simply be required before another layer is applied and leave it until the next day if possible before adding another layer - dont try and do 2 layers in one day.
Good luck - I really saw the finish come alive after the 3rd layer so see if you can keep it going....