I've made it with the 12 oz bag of Wilton Melts, 1/3 C clear corn syrup recipe. I added gel food coloring & Lorann oil flavoring to the syrup before I stirred it into the melts. Came out with tasty, vibrantly colored modeling clay that was easy to work, held its shape and people actually ate the decorations made with it instead of scraping them to the side of the plate like they've done with fondant!
I also used the recipe I found here on CC for Chocolate Leather. It calls for chocolate bark and clear corn syrup. Tastes just like a Tootsie Roll!
One thing I learned is to let the melted mixture set several hours before trying to knead it. I made a huge mess trying to sop up all the watery/oily looking goo before that lesson! OH! and it's a good idea to work over the sink
When did you add the gel and oil if I might ask? Was it during the melting process or when you folded the corn syrup in?