Here are all of the washes...
Gertsley Borate: (real Glossy, kind of acts like a glaze)
2:1 Water to Borate
Borax: (speckled shiny spots)
4:1 Water to Borax
Lithium: (eats through sig and underglaze. kind of like rust)
4:1 Water to Lithium
Soda Ash: (atmospheric, kind of speckley spots)
light: 6:1 Water to soda ash
heavier: 3:1 Water to soda ash
We also used Manganese, copper carb, black copper oxide and red iron oxide mixed with water as washes.
You can also try putting lithium in your slip. It will eat through the sig from underneath. This is much more subtle than applying a wash directly to the surface. try 2tsp lithium to 1.5 cups of slip