Gratia,
I have used 3oz of borax in 6oz of water when I am diluting the soap for neutralization.
To help you with some of your questions, since you want to use goat's milk there are a couple of tips/tricks that have seemed to work well for me:
1. a) Freeze the goat's milk in ice cube trays. this will help avoid the milk from getting cooked while adding the lye. Freezing lowers the temperature of the lye mixture to avoid discoloration. Freezing in trays keeps the milk in small, manageable pieces, instead of one large chunk.
b)When the milk is mostly frozen, pour the cubes into a large plastic pitcher. Place the plastic pitcher in a large mixing bowl filled with ice-cubes. Do not use glass in this step because the abrupt temperature changes may cause the glass to shatter.
c) Stir the milk until it is slushy and slowly add the lye in small increments until it is all mixed in. Try not to let the temperature of the lye mixture go above 90 degrees. The milk will still discolor a little but should still remain fairly light. The total mixing process should take 10 to 15 minutes.
2. As for diluting, I use the following:
Liquid soaps with high amounts of coconut or hard oils in them can be diluted in as much as a 40% solution. Soaps high in soft oils, like olive or sunflower, will start to congeal at as low as 25%. Most mixed recipes will do best somewhere in between 25% and 35%. Start with the higher dilution and then add more water if it starts to congeal or form a crust at the top of the bottle. Go slow, a little bit at a time, you can always add more water later. Taking it out is much harder!
Diluting Liquid Soap
% Actual Soap-----------Water Added per Lb. of Paste
15% -------------------------48 oz.
20% -------------------------32 oz.
25% -------------------------22 oz.
30% -------------------------16 oz.
35% -------------------------12 oz.
40% --------------------------9 oz.
Hope that helps you out, feel free to ask if you have any other questions. Good luck and Happy Soaping!!!
Tank