there is an advantage to mixing a base recipe dry and storing it dry. once a bucketful is mixed, it lasts indefinitely. when it is mixed with water, sometimes it is not used for some time and crusty stuff forms on the top or it dries out completely or gets so thick it has to be reconstituted anyway. lots of labor or irritation.
the biggest advantage, to me anyway, is that if the base is available and if it was originally called "green", i am free to try the base with other colors at any time i want. a ten gram (about a tablespoon dry) test of several mason stain colors lets me know which recipe is best for say turquoise or yellow without wasting lots of time or ingredients on something that won't work anyway. and when i do want the green, i just put a couple thousand grams into the scale and add the proper amount of copper carb to get it. that amount of glaze will get me through a lot of pots since i spray.
i guess this is what some of you get when you pay someone to mix dry ingredients and you add water when you get it in the mail.