Some people crumble the cake and spread it out to dry for a while before they make their cake balls. I've never tried it, but it might help. I generally forgo the icing as a binder and use the slightest bit of liquid - Bailey's is my favorite, but it might just be liquid coffee creamer. My cake balls aren't gummy, but they are a lot moister than some I've had (I compensate for that by adding a little shortening to the chocolate covering so that the shell is crunchier), although this may not be the texture you're after, either. I guess there's no way out but to experiment a little bit until you find something you like!
Marianna
"I know my own mind...and it's around here somewhere!"
Marianna
"I know my own mind...and it's around here somewhere!"