I used only the Simple brush and the smudge brush in the actual painting, then added some bluish tint with the single layer brush and a low intensity value around the highlight ray (to the background trees).
The simple brush was modelled after a paintbrush, with draw height reduced to 22 and alpha 7 used.
The technique is retentive after watching the Bob Ross method of painting when he had his painting series on national public television. I drew strokes for the background then changed color and cut in the ground plane, then the trees were added, single strokes and then drew in a basic color for the branches. Then a lighter color was used and gone over most of the branches to add volume and texture. Then the white was added on the trunks.
Then the smudge brush to blend in the various textures created along the trunks and branches.
Then additional highlights were added for volume.
Some additional rays and added tint, render adjustments.
Script tinkering nuked 2/3 document saves. 
I will have to get the script working to reproduce the middle state, since the final is already stored in jpg format. So if I can manage, I’ll post it. 