My gelding's get a grim/salty built up between their back legs under their tail and I always clean with water to make sure all the built up is gone, I run my hand up under their tails between their legs to make sure its all smooth and no grim is left behind, and they get really salty above their tails heads too. So I try to rise them of at least every other day, they love that running water in the late afternoons, its got to feel so good getting all the grim off of them.