The interior of our boat was varnished with a beeswax finish from the factory. When we purchased the boat the kitchen, bathroom, navigation table and main salon had sections where the finish was gone and the underlying teak had started to turn silver as it does when exposed to the elements.
In order to get our boat back to a factory finish we would have had to spend time stripping to bare wood and sanding that we simply didn't feel like we had. Part of the reason that it is a difficult task is that this is a very thin teak veneer and so sanding has to be delicate if done at all and a chemical stripper is probably needed. In addition, as a cruising boat we felt that we were not going to be able to keep the finish in that pristine state anyways so it would be wasted effort.
Instead, our goal was primarily to prevent any further damage to the wood and secondarily to improve the general look of the interior. As long as the wood is protected and sealed we can always come back and do a more vigorous refinish.
Just this abbreviated task took me somewhere in the vicinity of 60 hours of work in gloves and a paint ventilator spread out over several time periods. I used Epifanes Rubbed Effect varnish in clear with Epifanes thinner to match the existing matte look and I used foam brushes. I varnished the entire interior of the boat except for the salon table (to which we applied a wax treatment which has sealed the wood until we can, someday, choose to strip it) and the cabin sole.
I don't have any before pictures but here are the after ones.
Here is a section of finish that was in reasonably good condition to begin with (no bare wood) and to which I simply lightly sanded and applied a single coat of varnish:
Here is a section (post my coat of varnish) that also had no visible bare spots but which had thin enough varnish that it was absorbing humidity:
Here is a section that had dappled bare spots - this would have come out perfectly with more effort invested:
Here is a section in the head (where the shower water hits the most) that had large bare sections. I'm not certain if there is enough veneer to actually get this to factory finish. I did just a touch of light sanding:
And a section of the nav table with the same:
Not ideal but even so, the boat does look a lot better than before and now I don't have to worry about it getting worse and being damaged further. I no longer wince at any water I splash, on what used to be bare teak, when I shower or do dishes.