Advice of keeping persians clean after using litter box

Here recently both of my persians (who have always stayed pretty clean on there own) are both getting pretty nasty in back after litter box. I've trimmed their fur back there as best as I can but it's still not doing the trick. I've been having to bathe my really long haired one daily dorm a week. She tolerates it but she's getting more and more impatient with my daily bathing regime, especially when I have to spend 10 minutes on her back side.
I haven't changed foods or litter. Don't really know why this started. Any advice?

We actually have an article about this topic. Maybe it'll help?

 [article="32464"]Be Kind To Your Cats Behinds Dirty Cat Butts Prevention And Treatment​[/article]