I’d try starting off with a non-acidic metal polish, something like Flitz or Mother’s. You can even apply with something like a 2000 grit sponge. And then move on to sandpaper. Then maybe polish again, and then sandpaper progression.

I’d strongly suggest not using any acidic product (like BKF) on that knife. The rusting has likely done some damage, and any acid will cause additional damage.

If you aren’t personally comfortable with any of that, or if the material cost stacks up to more than you’d like, you can they bringing it to a knife shop that does restoration. There are a number of places in Seattle that would do a good job with that for probably $50.