Oh my, that is a problem. I'm not the best person to answer you either, but I wanted to commiserate!
I think this is the kind of thing they use the so-called "cone of shame" for - you know that plastic cone they put around pets' necks that keeps them from licking themselves? You might want to consider getting one. The cats will hate it. However, they can get used to it, it won't hurt them, and it will keep them from licking! I don't believe you have to go through a vet for this but you might. You could look for something like this first, though, at a local pet supply store, or online.
There might be something you could put on the fur that would be repellant to them but I can't imagine what that would be and it might hurt them, and anyway, no doubt they'd lick or rub it off right away anyhow.
