I love using Staining Colours and mixing in some grainy colours. When you lift of some of the grainy colours the staining colours will be exposed and they will glow. It is an optical effect you get with waterclours.

When you look at the orange an the bottom left image at the bottom of the left birch you will see the luminous orange glow.

Layering thin veils of paint will give you a luminous effect. Using a thick ,one layer of paint will not and the result can be chalky or muddy looking.

There is a place for opaque accents but not everywhere. Place them sparingly and keep your darks tranparent.