Hi again,
Some things that will help you to know:
- Painter 6 Watercolor brush variants are all included (along with many other new ones) in the Digital Watercolor brush category.

- They work pretty much the same way in Painter 12 as they did in Painter 6 (with the exception of changes in the program over 6 following versions).
- Of the top of my head, I can think of two ways to make Digital Watercolor darken underlying brush strokes:
- Dry the Digital Watercolor, then paint over the previous brush strokes again with Digital Watercolor.
- Create a New Layer and no matter what kind of brush strokes are on underlying Layers, the new brush strokes painted on the New Layer will darken any visible underlying color.

You'll need to experiment with each of the Digital Watercolor variants to learn whatever else needs to be done to make the brush variant behave the way you want. What I've explained above is just basic information.
One more thing:
When Painter 7 was released, the Painter 6 Water Color was gone and replaced with new brush technology. The main thing that remained was the Method: Wet used in Painter 6 and in the new brush technology for Painter 7 Watercolor. (Notice the different spelling in each Painter version.)
Users were pretty upset to see Painter 6 Water Color gone so in Painter 8, Corel introduced the new brush category, Digital Watercolor. This brush category as mentioned above contained all of the brush variants from Painter 6. The main difference was that Digital Watercolor used/uses Method: Digital Wet and there are more brush variants in this brush category.
Hope this has helped and will help you.
Happy Practicing!
Jinny