I decided to try several things that were unfamiliar to me all at once. I painted the same picture on an acrylic background, using gouache; watercolours; and watecolour pencil. Not happy with the results, but I've learned a few things. First of all, the colours bead up on the acrylic -- though it happened least with the pencils, because I used a very small amount of water just to dissolve the colours which I had put on dry. Then, I wasn't able to get intensity from the watercolours at all. And the gouache, though it went on darker, somehow turned to mud. I might add that I'm not good at painting flowers in the first place - so that's another part of the experiment. Well, anyway, here they are, my blobby flowers:
Gouache on gold acrylic
Watercolour on gold acrylic
Watercolour pencil on gold acrylic (my acrylic layer was thinner and smoother for this one, which may have helped the pencil to adhere more smoothly)