Years ago I picked up a bunch of pretty blue toilet bowl brushes for 99 cents apiece. My Mom pricked my bubble by saying "no one uses those anymore!"
So I sit with these pretty brushes...finally, after making cat cages, I noticed the cats keep rubbing on the wire. I found one of my blue wonders and put it to use by cable tie-ing it to their cage.
See the whole maze of cat walk on my other instructable. If they need encouragement, add some catnip to the bristles.