I test this bubble-tracing and i think that perhaps it is idea to present it tips-tricks forum. This method gives easy path to found colors and mix it also by using tracing image.
"Idea/year keeps man/woman on the road.... hmm. or not. "
Step by step.
1. Load tracing image.
2. Rescale paintint example 1600-1200 or what size you need.
3. Edit tracing image - scale - stretch image to fill.
4. Use oiltool that down layer.
5. Dublicate layer.
6. Use knife that second layer.
7. Add new top layer.
8. Use glitter-tool of that top layer.
And then found many new wonderfull colors.