Waiting 24 hours between each coat of paint on trim allows the previous coat to dry evenly and smoothly. This ensures that each subsequent coat goes on just as evenly and smoothly, avoiding distortions in paint color and surface texture.
Before applying the first coat of paint to trim, even out the texture of the trim by sanding with a fine-grit sanding sponge. The sponge conforms to the shape of the trim better than sandpaper and gets into the crevices and edges of trim pieces. Wipe the sanding residue before trim is painted. After the 24-hour wait, repeat the sanding process with each layer except the final one.