I have made the same bad experience with the Dynarette. After a short while the shellack sides of my guitars got really dull and worn out. Luckily Andrea Tacchi gave me a small bottle of his polish (not the shellack) and a a cotton pad to rub it in. From time to time I treat back and sides with some drops of the polish and it is amazing how it cleans up the surface. Looks like new afterwards.
The secret of getting ahead is getting started (Mark Twain)
Andrea Tacchi, Enrique Garcia model, Spruce/BRAZ, 2016
Giovanni Tacchi, Daniel Friederich copy, cedar/EIR, 2017