My last Shop Talk Live Stream was about a finish called Royal lac and I had Vijay Velji from Shellac Finishes. on the stream to discuss the benefits of this product and show one application method. Vijay created the finishing product called Royal Lac. Over the years I have done extensive testing of this product and found it to be a viable finish for instruments. Basically it is a shellac based product that forms a chemical bond after application that is similar to polyester. It comes in regular and catalyzed versions and can be applied in a variety of methods: padded, sprayed, brushed and French polished. 
Below are some pics of a couple of sample boards I did recently using the original version of Royal Lac. (It also comes in a post catalyzed version that can be leveled and buffed in 5-7 days!) One was a spruce board and the other was Wenge that had been pore filled with Zpoxy. I applied the Royal Lac using my French polish method   Both boards were done in about 1.5 hours. Look at that build and shine! Even though this product is shellac based it offers much more scratch and ding protection than traditional shellac. 
 
 
Vijay is a chemist and has developed a wonderful product for us luthiers. He is very accessible and can answer your questions about Royal lac and finishing in general. He offers Royal Lac as well as traditional shellac on his website.