You or a groomer can clip the hair around the arse so you don't get caking on the fur.

Your vet can do it to.

The only real solution is to trim it back. It will look just fine.

I have dogs that need a good butt trim so it doesn't get messy back there.

Also, baby wipes ;-)

http://www.amazon.com/Wahl-Professional-Animal-Grooming-9484-300/dp/B00A8D95OG/ref=sr_1_3?ie=UTF8&qid=1451067597&sr=8-3&keywords=dog+clippers

Have her rear-area shaved.

At my groomer it's called a "sanitary trim." :-)

Very carefully.

You can, while she's still friends with you, get some pet shears with rounded tips. They are sharp (you want sharp). In between praise and ear rubs, you can coax her into letting you hold her and carefully (but don't dally) trim a lot of the pantaloon area. I had to do this with a dog. I bet there are people EHO need to get such a trim. I don't know any, but I'll bet they're out there.

Cat sleep with you?

I also snip the fur with small scissors while someone else distracts his front end with a treat. I will say it is unusual to have the problem and he is really fluffy.

Frequently Mineral Oil will help "dissolve" any stuff back there. I've used it on days old puppies with zero adverse affects.

Baby Wipes? Also Trim it down, you can get a cheap pair of trimmers just for your kitties booty.