Morgaine, It is so wonderful! It has simplified and speeded up my soap making time like nothing else has.
If you get oils in 5 gallon buckets, keep those to use for your master batch. If you don't get oils in 5 gallon buckets, get to a big box store (home depot, menards, lowes). They sell them there (with lids) pretty inexpensively.
When I make soap, I like to fill all my molds ... 2 of them take 9# of oil, one takes 6# of oil. So every time I want to soap, it's 24# of oil ..... I think each 5 gallon bucket will hold about 25# of oil, sooooo I go to my lye calc and find out how much of each oil I need for 30# of soaping oils. (I have three 5-gallon buckets). I weigh up each of my solid oils in my stupidly big SS pot and melt it. Weigh up my liquid oils, then add them to the solid oils once they are melted.
I pour about 1/3rd into each of my 5 gallon buckets. Then I do it again so I have a total of 60# of oils. I mix real well, then set in a cool place. Since I don't use palm oil (which can and will separate), my oils homgenize together nicely. If I used palm, I would set them in a cold place so they would cool off immediately without separating and then store in cool place so it would not melt. If it does melt on you, just stir with a long paint stirrer.
When it is time to soap, I measure out 2 pots of 9# of oil and one pot of 6# of oil. You can start soaping immediately without having to measure each of your individual oils for each soap batch.
If you don't have room to store your soaping oils between soaping, and say you have to make 6 batches of 3# of oil, instead of weighing each recipe on it's own, weigh out the oils for 18#, then weigh out 3# for each batch.
It's really great for room temp soaping, since the solid oils are already mixed with the liquid oils and the solid oils aren't as solidified. Makes the melting from the heat of the lye solution work much faster.
It really speeds up the time in making soap! Let me know how it works for you, if you try it.