The sanding smooths any imperfections in the existing surface and adds tiny scratches to enhance adhesion but it's probably not necessary to have every square millimeter abraded.

Thanks that helps - it's been a week since first coat went on, I don't know if length of time has anything to do with how aggressive of sanding I would need to do.

The better job you do at micro abrading the first coat, the more likely too that the new second Bona coat will adhere without bubbling. Don't forget to wipe everything off too. I think Bona suggests with a slightly wet soft cloth, ensure dryness, before applying second coat.

It does NOT need to be uniformly dull. The point of sanding is knock off the high spots. The next coat will look the same over both the dull and non-dull parts.