Well I think I'm getting there. So far I have done the following.
1. Cleaned and sanded the surface
2. applied a wood stain
3. Used regular wood varnish
4. 24hr drying in warm dry cabin.
5. Sanded out with 320 imperfections in the first coat.
6. Heated up varnish and applied 2nd coat
7. 24hrs later, suffer surface with fine scotch pad. And again let sit for another 12hrs
8 heated up varnish and added some synthetic thinners to varnish. Applied and its now looking nice.
9. Will now leave for a week to fully cure and then polish with the recommended car polish.
Does all that sound OK.
Close except for step 9, which will probably be a bit more drawn out than you planned.
To get something like a mirror finish:
a. Sand level (I'd wet sand) working up through the grits to P1000 or higher.
b. Polish up using car automotive polish like T-Cut. For the full effect, move up after that to finer grades of car polish like Swirl Remover.
But this only works if your varnish is fully cured, and that might take 4 weeks or more. The initial test is to dry sand gently - if the paper loads up immediately, you need to wait some more. If you don't level sand then you will end up with a nicely polished corrugated surface, which isn't the look you're after.
After sanding, clean off the surface and look across the surface towards a light source. If it's uniformly dull, you're good to go up to the next grit. If (initially) you see any shiny spots then they are lower than the rest and you need to sand some more. Once your first sanding has produced a truly level surface, the later sanding will be much quicker - again, use raking light to check you've removed the old sanding marks (hint, for each sanding sand at 90 degrees to the previous, that way you can see when you're done). I'd probably go P240, P320, P400, P800, P100 (maybe higher).
For varnished musical instruments, some varnish recipes need 2 or 3 months curing time, but I suspect your wood varnish will cure quicker than that. But if in doubt, leave it a bit longer!
