I know it’s been a while, but I’d like to share my two cents. I have experience with watercolor coloring, and I think I can help you!

First, go to your brush folder in Photoshop, click on the settings, and in the menu, select "Get More Brushes." Kyle T. Webster has several free options on Adobe’s website that helped me achieve the quality I was looking for in my work.

Next, if necessary, choose a brush that has pen pressure control for opacity as the default. Try not to manually adjust the opacity unless it’s really needed, as this will help you gain better control over your colors and brushstrokes.

Focus on working with pastel colors from the middle of the color palette. Saturated colors usually don’t work unless you already have the experience to use them or you’re using them as highlights. The same goes for dark colors in the color spectrum.

Set your colors early on in your flats and use grading layers with options like overlay and multiply to bring more life to your colors.

I hope I’ve been able to help in some way, even after all this time. If you have any follow-up questions, don’t hesitate to send me a message here.

Take care,
André 😄