Why does primer need 24 hours? Adding coats of primer or paint too soon could cause the paint to wrinkle. For the best results, spray all your primer coats on the piece within an hour. If you don’t have the time, wait at least 48 hours to apply a new coat.
Should you let primer dry first? As Phillips mentioned, you want to wait a full minute or more to allow the primer to dry completely before going in with makeup, as this will help to curb pilling or patchiness. Another mistake people make is choosing a primer that’s wrong for their skin type.
Can you prime and paint in the same day? Priming then painting on the same day is doable only if you work with latex-based or shellac primers. On average, these two primers take about 1-3 hours to dry per coat. On the other hand, if you are using an oil-based primer, you would need to wait for 4 hours up to a whole day for the coat to dry.
Do you ever need 3 coats of primer? As long as the primer applies uniformly over the previous color, then one or two coats should be sufficient. Again, it is not necessary to apply several coats of primer to try to get a perfect white finish. That is the job of the topcoat (paint) which has to be applied on top of the primer.