I have a system of feeding my newts in jars and it works very well, for keeping the worms in one spot and for cleaning. Also, the newts now know their food comes in the jar so I can offer different foods to them and they at least know they're supposed to eat it, whether they like it is another matter...at least they try it. That's how I got them to try bloodworms and to try cut up shrimp. Here are some visuals of the jar system. You can leave the jars in for a few hours, or overnight as I sometimes do, or until the next time you feed them as I also sometimes do (because they clean them out!). Also if there's just a little waste left, the snails get to them and I just let them clean out the pieces, and then if there are too many snails I have them all in a jar for easy disposal! (little do they know...heh heh heh). For my Tarichas, which are bigger animals, I have a glass baking bowl that you can see in the last picture...it's larger and that way they're not too crowded in there and biting each others' hands and feet.
This method isn't so good for foods that float, however, because they'll just float right out of the bowl and away into the tank. Hope this helps!