The vet should have bathed him for you.  You can use any sort of
moisturizing shamoo, or Nature's Miracle Cat Shampoo or Skunk-Out, but
make sure you avoid his eyes and face.  Once he is dry you can brush
some cornstarch-based baby powder (NOT the talc kind) into his fur to
help with the smell (they make a lavendar scent that works pretty
well).  Other than that, you really need to let it wear off.

-L.