When a cart is 'dead', use the normal safe cleaners first, though a good bash of automotive/hospital cleaners can often bring the cart back. (scrubbing with stiff toothbrush or steel-wool is good too!)

You'll be pretty gentle at first - but after a while, you'll be using almost destrictive force cleaning carts like the rest of us. Remember though to then clean the cleaner off. You don't want the nasty cleaner on there for good, so use the standard contact cleaner afterwards with a clean rag to wipe away nasty residue.