depending in the type of finish on your watch, if its brushed, use very fine grid sand paper (always experiment first)
if its polished then use stainless steel polishing liquid
but if you are not confident enough, just send it to the watchmaker...
any jewellery shop will tell you they can do the job... they'll just send it back to the AD and charge you a higher price.
On the other hand, what do you all use to polish acrylic crystals? can i use car scratch remover to polish?