Handy guide for painters I thought, came in the white dwarf a while back, but not always accessible if you don't have it on you.
https://www.games-workshop.com/resources/PDF/Downloads/CitadelPaintingSystem.pdf
This is a link to a basic guide on how to use the differing types of paint.
https://www.games-workshop.com/en-GB/Citadel-Paint-Guide