One of the items I noted was using a sculpting tool to shape the blob, but I also use an X-Acto hobby knife to remove excess material. I've since found that it is easier to shape the blob, but not cut off the excess right away. I let it harden a bit - say waiting at least an hour - and then come back with the knife and cut off the excess. This does two things:
- Makes more of a cut, rather than a tear, of the material.
- Less chance of the whole blob popping off of the wood as it has had some time to adhere to the surface.