I guess my method is a wee bit simpler. But might not suit all!
I normally brew a 28l batch.
For most of my beers, this will be 5kg grain, or a bit less.
I mash this in 12-13l water. I then transfer the mash to a separate sparging bucket & keep percolating hot water through it. I do not bother to calculate any volumes - but I do know that the boiling pan I use has a volume of 22l up to the handle rivets, and I don't usually go more that this.
I do taste the spargings occasionally. By the time the boiling pan is at 22l, I have always found there's no residual sweetness (and no hint of harsh bitterness), so I stop there. I used to get about 70% efficiency with bought crushed grain. Now I have my own malt mill, and mill finer than before, then 80-85% is normal.
After the boil, I must obviously have less than 22l. I leave this to cool overnight, then pour it with vigorous aeration into my primary FV. I dilute this with tap water to 25l & ferment for about 4-5 days, ideally. After this, I transfer to a 2nd FV, add dry hops (well, sweated hops in the extra 3l of water to make up 28l), purge with CO2 and leave for a target 10 days.
Works very well for me........