This is for the MP17x series primer (MP170, MP171, MP172) It depends on the number of coats and the temperature. P-sheet says 1 coat @ 70 F is 15 minutes dry time, 2 coats @ 70F is 30 minutes. Colder temps will increase dry time, hotter temps decrease. I do the touch test - wait the specified amount of time and then touch the paint in a hidden area. If it's sticky, wait another 10 minutes.
You've got 72 hours @ ideal temps to get a top coat on top of the epoxy primer before you have to scuff it and re-shoot.