If you can't wait, microporous paints allow the plaster to release moisture and breathe while still drying. Typically, microporous paints are thinner than water-based and solvent-based paints, so once the surface is dry, I recommend painting over them with emulsion. Remember, only add the extra emulsion coats once the fresh plaster is bone dry. If you plan to use microporous paints, read the product's instructions for thinning and applying mist coats to fresh plaster. Although microporous paints are viable if you're in a bind, I highly recommend waiting for the plaster to dry out completely before painting.