You can use a rack cleaner such as Rack Attack by Trebla and
there are others on the market as well. You can also use Lysol
toilet bowl cleaner but only use in a well ventilated area and
rinse thoroughly with lot's of fresh water. If the gears and
other parts are just stained that's normal and there is not much
you can do about it, they will not remain bright red as when new
and the staining is of no consequence except for being cosmetic.
Build up is another issue altogether and must be cleaned off.