for things like surface scuffs, glue/adhesive residue etc you can try
non-acetone nail polish remover. that usually works very well in my experience... i've used it on my lv vernis bags and it works wonders. i would test it on a small spot first, just to make sure it doesn't dull any of the finish (but i never had that problem).
however, if that doesn't work, and if it's like an ink stain or some sort of color transfer (from clothes, etc), i am 99.9% sure there is nothing you can do to get it out. sorry! because when that happens with inks/dyes is that they get *underneath* the shiny surface, so nothing you put on it will be able to take the dye out.

i know it sucks, thats why patent leathers are so high-maintenance (i luv it anyways though

)