Oil and Water Do Not Mix
You surely know this, but we cannot stress this enough; you cannot mix oil colors with water because these two substances repel one another.
Fat over Lean
Some paint types contain more oil than others. The more oil they contain, the fatter it is, thus the slower it will dry.
Generally, the rule says that you should make sure that the top layers of paint are “fattier” than the ones at the bottom to avoid cracking. Because if you do the opposite, then the layers on top will dry faster than the ones below and cause cracks in your paint.
Thick over Thin
This rule is similar to the previous one. As thick paint dries slower, it should be on the top layers to avoid cracking