I am learning new things all the time, although the "layer" thing still confuses me a little. I did try and paint in multi-layers for a few portraits, but I got frustrated when I forgot which layer has which. If you try and paint in an area on the wrong layer, it doesn't work very well. My last few portraits have been done on a single layer only.
The two images below show an early stage and completed stage of a Samuel L Jackson portrait that I completed recently. I 'borrowed' the colour tones from the original little thumbnail that was copied into the picture canvas. I then had a palette to work from.
Only three brushes were used. I favour a rough brush that simulates brushstrokes that an oil painting filbert would make. This was used right down to one pixel size. The other brushes were a blending tool to smooth out areas and a special brushes that creates dots across the painting. I used this for painting fhe skin pores.
Hopefully, if you look close enough, you will see the result of all three of these brushes in both the pictures below.
And her is a youtube video of the final stages . . .