My methodology may seem complicated, but it is really very simple.
To make all grain work for me, I took copious notes for my first few batches about temperatures, time, and volumes. It took a few batches, but I learned my evaporation rate and grain absorption, which is crucial to hitting the right volume (therefore the right gravity).
Vb = (V1 + V2) - (Et)
Vb = volume at end of boil in gallons
V1 = volume of first runnings in gallons
V2 = volume of second runnings in gallons
E = evaporation rate in gallons per hour
t = boil time in hours
But how much do you need at the end of boil?
Again, work backwards.
I want 5 gallons of beer in my keg.
That means I need about 5.5 gallons in my fermenter.
Which means I need to have 6 gallons at the end of boil (after hop absorption and cooling losses).
Which means I need 8 gallons before I boil for 60 minutes. This is a relatively high boiloff rate, yours may vary.
I batch sparge with one round of batch sparging. This means: I mash, then mash out, then lauter first runnings. Then do one batch sparge.
I usually use 1.5 quarts/pound of grain because it is easy to calculate, but on higher gravity beers I will use 1.25 quarts/pound to keep V1 from getting too large relative to Vb.
For example, let's say I have ten pounds of grain. I will add in 15 quarts of strike water (3.75 gallons).
I mash out at 168. To make things easier, I use the "adjust mash temperature" calculator on beersmith. If my mash is 152F, I adjust the addition temp until I get a round number. To get to 168F, I need to add 1.5 gallons of 198F water.
That means I now have 5.25 gallons of water in my mashtun. The volume of first runnings (V1) can be predicted in the following equation:
V1 = (S + M) - (xG + D)
S= volume of strike water in gallons
M = volume of mash out water in gallons
x = grain absorption coefficient in pounds per gallon
G = pounds of grain
D = mashtun deadspace in gallons
I initially went to the trouble of measuring my mashtun deadspace, but then I realized it is unnecessary. Before I dough in, I add a gallon of boiling water to my mashtun to preheat it. I then run that hot water out of the mashtun while the strike water is heating up. Once that preheating water is run off, the mashtun deadspace is now full of water, eliminating the variable.
After several batches, I have learned that my grain absorption coefficient is 0.11 gallons/lb grain. That means I will lose 1.1 gallons in 10 gallons of grain. Referring back to the first runnings equation:
V1 = (3.75 + 1.5) - [(0.11)(10) + 0 ]
= (5.25gallons) -(1.1 gallons)
= 4.15 gallons
Now I know the volume of my first runnings without measuring. If I know that I need to boil 8 gallons, then my sparge volume (V2) is 8 gallons minus 4.15 gallons (V1) which is 3.85 gallons.
I then add 3.85 gallons of water at 168F and start lautering immediately. With my SS braid, it takes about 10 minutes to completely run off all 3.85 gallons.
Now I have 8 gallons of wort at the right gravity ready to boil. To ensure that my evaporation rate is correct, I take refractometer readings every 15 minutes and adjust my flame to compensate if needed. For example, if my preboil gravity is 10 brix and I need the OG to be 14 brix, every 15 minutes of a 60 minute boil, the wort gravity should increase by 1 brix.
Hope this makes sense. Please ask questions if it doesn't.
Eric