I am wet sanding the varnish on my Night Heron, which I have paddled for one season, to add another coat or two of varnish to get ready for the upcoming paddling season. I am using 220 grit. I understand that the surface should have a dull look in areas I have finished. I have completed sanding one side of the hull. As I look down the hull, I see shiny spots here and there - a fair amount. My question is: do I need to go back and sand out all these spots in order to get an even coat of new varnish?