1 for how long do you batch them to get the best results?
Overnight. Make sure the temperature is at least 70°F. Letting them react for longer than necessary prevents backstaining of dye from one section to another, when you wash out the excess dye afterwards.
2 do you batch them tied or untied?
Leave them tied until you're ready to wash them out. Rinse them once in cold water and then wash in HOT water (140°F),
3 how and when is best to add the soda ash in low water immersion dying?
I like to let the color creep around on the cloth for an hour before adding soda ash. Add soda ash at the beginning for less color separation. Try it both ways.
Paula