it is best to use benzine. If you are talking about a more serious blemish, you will need to use a boron-carbide type of paste but it is best to let the Panerai service centers handle this.
I myself got a IWC top gun which is also in made of ceramic. I found the problem is the watch can be scraped over from other metal which would leave marks on the watch which is really hard to get it out. I am not sure if that would happen to the 317 owner...
it is best to use benzine. If you are talking about a more serious blemish, you will need to use a boron-carbide type of paste but it is best to let the Panerai service centers handle this. Cheers, Asi