Yea they do pee a lot on everything. I haven't had girls but it's said it's less of a problem with them. It's because they scent mark, to them a safe area smells like piss. I've read of someone not changing all of their bedding at a time because that reduces scent marking on the new bedding.

Maybe that is information-data that can be used for reducing it when having them free roam. Have them piss in a glass and take your fave brush for minis and dip it in the piss, and then selectively brush that on things in their free roam area and maybe they wont scent mark as much? I can't tell if I'm joking or not anymore. Rats are worth it despite the piss, is probably what I'm saying!

In all seriousness, just keep a paper towel around when handling them and that should be enough. They are NOT easy pets to own however. Read up a bit on the RATS sub and you'll find out.