You can proceed to the next glassing step as soon as the resin hardens and you're able to sand it (for example sanding down the laps to the foam).
Resin curing times depend on type of resin, temperature and humidity so use your good judgement before moving forward.
Trying to rush to finish a board rarely ever works out and creates more problems that prolong the build. Believe us. we've rushed plenty of experimental shapes for swells on the way and they more often than not sat on the glassing racks while surfing the swell with an older board... that's how it goes.
We do however recommend waiting a day to sand the board after the bottom hotcoat. It cures up a lot harder and sands nicer...