I am just finishing up (no pun intended) polishing the finish on my boat. I am not using a polisher - just buffing by hand. I used Interlux Perfection varnish.
I start with 400 grit to level out the finish and then go through 600, 800, 1000, 1200, 1500 and 2000.
The biggest difference after 2000 grit is how much smoother and slick the finish feels. I started out doing a small area on the hull to see if I wanted to do the whole boat. I liked the feel enough to put the time in for the whole boat.
The gloss level after 2000 grit might be similar to what you have now with satin finish. It is not as glossy as my unsanded perfection. To get the rest of the way, I am using a progression of Meguiars polishes where the last step is a layer of wax. Then I buff on a coat of Meguiars Final Inspection.
And yes, this is likely a complete waste of time once I have paddled for 10 minutes. I suspect that this project is a little different for me than most. I have been working on my King for 5 1/2 years. It has been strictly a spare time endeavour. I have told my friends that it is an art project that will end up as a kayak. For me, the polishing effort is like the last step of the "art project" phase.