Leave the second coat to dry for approximately 25 to 30 minutes, depending on temperature.

When should I apply second coat of plaster?

Apply plaster

After devilling or scratching the first level of plaster you can apply a second and final coat. This should be of a thinner consistency than the first coat so make sure to dilute the plaster mixture with some more water. Aim to only plaster a thin 2 mm layer. Then leave the plaster to dry slightly.

How long do you wait between skim coats?

Let the joint compound thoroughly dry before adding more.

It looks dry. It feels dry. It may even feel dry enough to sand. But unless you're working with the chemical-hardening stuff (that has a much shorter curing window of 20, 45, or 90 minutes), you need to wait 24 hours before applying a second coat.