I found that using a very sharp knife to score the plastic, then carefully tearing the image out worked the best.
I'm very new to this and haven't done all the reading on the very many ways you can make this yet, so I have a question. How are you able to tear the image out? Is the paper a lot more pliable than the #6 plastic you find around the house? Or do you tear them out after you've shrunk them?
What blade do you use? Is it the really thin, needle like X-Acto blade?