Okay, the general consensus is to sand between coats of varnish with around 220 grit, wet or dry.
What about after the final coat? You still might have dust nibs to flatten out, maybe even a run or a sag, but you don't want to scratch the surface up too much.
I'm using satin finish polyurethane, so I probably don't have to go as fine as someone looking for a smooth glossy finish.
After my final coat, what grit should I start with, what should I end with, and how many different grits between?
What about runs or sags? Start with a coarser grit and work my way up?

Thanks in advance.