Once the fabric is dry, the paint can be heat set and becomes permanent, so there's a choice to blend paints right on the fabric by spritzing with water, or heat setting the first layer and then overpainting with a second color. Since I know I'll be cutting up the fabric for applique, I usually try a few techniques on the same piece of fabric.
I also worked a bit on this piece of cotton fabric which I had previously designed with a paint masking gel (I can't find the tube to tell you the brand) and a fine Sharpie (waterproof) pen. The gel parts I'll paint over with acrylic paint, let it dry for 2 days, then wash the fabric to remove the gel. The Sharpie designs I'm painting in with my fabric paints, which I will then heat set.
This is all absolutely playful experimenting for me, and I love it!!