The best way to clean the valves is with a walnut blaster. Sand blasting would get sand where it shouldn't be. I just used a gun barrel cleaning brass brush, a shop vac, some dental pics, lots of carb cleaner and one hour per set of valves to clean all the crud. It makes a big difference if you have a lot of buildup. Just make sure the valves are closed then fill up the chamber with carb cleaner and wait a bit before you go to town with the brush. It takes lots of patients and working at odd angles.
Nice writeup BTW