I am only planning on using the orbital to clean off old varnish and get down to bare wood, where I need to.

Then I will go with a finer grit to smooth things out (200 grit... sanding by hand with a soft block in the direction of grain), then I will apply varnish, and after it dries, use only the finest grit (I am using 600 wet/dry) to "touch" that varnish layer, before applying more coats... repeat as needed.

Does that sound about right?

I also vacuum and use a tack cloth and/or acetone on a rag to "clean up" prior to applying the first coat of varnish. (the acetone dries out the wood a bit and the varnish really gets in the "pores")

I am doing this a bit at a time (like painting the golden gate bridge) and working the most beat up areas first. Eventually I plan on making sunbrella covers for most of the brightwork... yeah, it is a labor of love...

I see some advantages in a full boat cover, but I am currently thinking to just cover the brightwork alone. I have solar power vents on the boat and I want to keep those active.