The worst part is waiting for it to dry between coats. I usually did one color a night, maybe two, no hurry.
Handy tip for all, you can speed up the drying process if desired by setting a fan to blow across the work. Paint or glue or anything else that needs to air-dry. Even letting a fan run overnight will have things a lot drier first thing the next morning than if a fan hadn't been used (ballasting track with 50/50 white glue & water mix would be one such good example for overnight drying).