Hmm… I’ve just been trying things out on the green fabric. It’s very dark, and the red and yellow paint just aren’t showing up. The white paint is OK, actually, but I’m having to accept that this cotton and this paint just isn’t going to work for what I wanted to do.
I’ll wait & see how the paint dries, to see if that makes a difference, but I’m thinking it probably won’t.
So that means EITHER I do what I wanted to do but with different fabric, or I do something different from my original plan.