Maybe try bar keepers friend or Brasso very carefully

The GoLo putter is made of 303 Stainless steel and Aluminum according to the website. I doubt that the stainless portion of the putter is rusting as 303 stainless contains very little carbon steel, carbon steel will rust.

My question wouldn't be "how do I clean the rust off" but, my question would be to Scotty Cameron as to why you are seeing rust on a stainless steel and aluminum putter?

The only thing I can think of is that the weights may have some carbon steel in them or the threaded inserts for the weights is made from carbon steel.

I would talk to SC about this issue. My $.02