Yeah, I've never been able to get Surbufs to finish down in a single step. Pretty much always have to go back with at least one more step.
If it were me I'd have skipped the D300 step and tried either 205 or 85RD on a MF finishing disc -- you might find you don't even need the third pass that way.
I wanted to make sure this one turned out nearly perfect so I spent a lot of time on it. May have gone overboard but I had to.