There are so many different ways of finishing musical instruments that I am not going to show much here. There are all sorts of varnishes and lacquer finishes, plus various oil finishes, and of course good old shellac french polished. There are also different ways of filling the pores, and different methods of application. Books have been written on the subject, and there is much discussion on Internet Luthier forums about finishing. All work, and all have strengths and weaknesses. A french polished finish I believe is the most beautiful finish, is easy to repair, but it is not very resistant to sweat damage. I use an alkyd oil varnish manufactured by Target Coatings and sometimes french polish on top of that. I like it because it is an exceptionally flexible finish that I think sounds great on my mandolins. Other Luthiers get good results with different products. Finishing is something that takes a lot of time to get a great finish, sometimes even as long as it takes to get the instrument to the stage of ready to be finished, so patience is required.
If you are really keen to know the details on how I varnish my instruments, I have finally written a paper on it which has been published in JAAMIM. You can read it here.