I'm working on a project, inspired by an article I read in Pottery Making Illustrated.  It's a lowfire bowl with layers of underglaze using a wax or latex resist

I started with a black layer of underglaze.  I cut a fish silhouette out of paper and used that to protect the black as I painted blue over it.  I just kept moving the same fish and painting around it.

Then I used latex as a resist over each of the fish.  I like latex better than wax, because if you drip it in the wrong place, you can just peel it off, unlike wax which is permanent.

Then I added blue fish, by putting the stencil on the blue areas of the bowl, and painting black around them.  I also carved through the underglaze to add eyes, gill plates, and a latteral line to each fish.

It's difficult to take a good picture of the results, because the bowl is shiny.  These pictures are after the second firing, so they already have the shiny overglase on the piece.  I'll take a better close up and put it up on the site too.