We don't have a Kong (no rubber toys here...because of my picky two)...but from past topics regarding this....the top shelf in your dishwasher works well and the baby bottle brushes (I think someone mentioned a double headed one - bigger brush one end and smaller brush the other end).
I bet you can do a search here on YT and type in Kong Recipes and find tons of them! I think I remember seeing some threads started about this awhile back.
Here's what I found for "stuffing your kong":
http://www.yorkietalk.com/forums/sho...t=kong+recipes http://www.yorkietalk.com/forums/sho...t=kong+recipes http://www.yorkietalk.com/forums/sho...t=kong+recipes http://www.yorkietalk.com/forums/sho...t=kong+recipes