I use that same exact cup for my 1y/o panther. It works well for him, and I have seen many breeders use it. The key to cup feeding is placement. Try experimenting with various locations, but always keep it low so it can see inside the cup. Sometimes having it under a basking spot, or "nap" spot will do the trick. I find that my cham will crawl to a particular spot where he retires for the night, but before the lights go out he will take another zap at a meal.
Another better option is to use a tupperware container that is wider and shallow, thus promoting more movement from your feeders. This works well for others as well.