Many paint manufactures claim their paint will cover in one coat, particularly the paint and primer in one products. I used to think this was a joke until I started checking my mills during application and trying to put it on at the recommended thickness. It really will cover in one! I just finished a big interior job where the existing wall paint was dark red enamel. We put one 4mill coat of a light beigh colored ValsparUltra and it covered perfectly! Since I have started applying paint at the recommended thickness the results I'm seeing are amazing! I painted for 15 years and never really thought about how thick I was putting it on. Proper film thickness is essential. This realization has been a huge boon to my business. After all, we pro painters are selling coatings and the application of coatings, not knowing how thick these coatings are supposed to be seems ludicrous.