How long do you leave plaster between coats?
Likewise, how long do you leave first coat of plaster?
After the first coat of plaster has been applied, wait approximately 20 minutes in order to let the plaster dry slightly. You can then get rid of lumps and bumps by smoothing over with the trowel. You also need to smooth out all the corners and ends such as the bottom and top of the wall.
Besides, do I need to PVA between coats of plaster?
The correct mix for pva for plastering is 1 part pva to 5 parts water, and really only used to stop the plaster drying too quickly, plastering over silk paint with or without pva can only be as adhering as the paint before, pva doesnt make the plaster stick to the behind of a painted surface!
You can tell when the plaster is dry by watching the colour change. When the plaster has a uniformed pale pink complexion then you can firmly say it's dried.