Any recommendations for products and procedures to use for slide scratches and blemishes regarding the Coyote Tan finish on the M17 and M18?

I know of no touch ups for the finish.

What I would do is send it of to a refinisher like our forum member CCR/Cummings Custom Refinishers and have a more durable finish applied.

While I have not seen or held your particular slide Sig came out with a tan P229 Sport slide many years ago that was the absolute crap. They were limited release and looked nice when new but were the worst looking thing with any kind of wear/use. I almost bought one new but started seeing complaints and pictures of them used and they were the worst looking guns I have ever seen.

Contact Mary or Brad at CCR and they will hook you up. They run discount sales pretty regularly here in the classifieds that will save you some if your willing to wait.