Not sure how many people use iBrewmaster, but as someone who owns both iBrewmaster and Beersmith 2, I like to go the lazy route and formulate recipes on the iPad. The downside to that is the mash schedule portion of iBrew is lacking to say the least, there is no obvious way to setup for and batch sparge and not much on the internet on workarounds. While playing around today I figured out an easy way to get the calculations right with minimal fuss and thought I would share it to save anyone else the headache.
The first step is to know the boil size your shooting for in the kettle, and to make sure you have entered MLT dead space in the mash profile.
Next in the setup menu go to mash steps, and add a new step. I named mine 5G 60M Second Runnings, to denote the batch size and boil length, longer boils require more starting volume. For options select Freeform, Infusion,Volume, and under water to add enter half of your boil size, in my case half of 6.7G is 13.40Q. I set temp to 168 and the rest blank.
Now that you have that done, add your recipe as normal, including adding an auto calc mash step for the body desired, this will give you your initial amount of strike water and strike temp, and was where I was basically stuck before. Add second mash step, the one you just created, you will change the order later. The third step it to add is the on labeled autocalc sparge.
Once added iBrew will calculate the absorption of the grain from the first step, in addition to the second runnings from the custom mash step, and give you the amount of water that should be added before the first runnings to get equal first and second runnings, which is like most things in brewing, arguably the best for efficiency when batch sparging.
Under the mash section you now have step 1, then 3, then 2. To fix it click the autocalc sparge step, change to freeform, and drag it up to position 2. Now the mash schedule has the correct amount of strike water, the additional mash out water before second runnings, and the water needed to get a second runnings amount equal to the first. Definitely not the most intuitive way but once you add a mash step for each batch size and boil time iBrew does a decent job of calculating the mash out volume. If you get a negative number for sparge water on a large grain bill, simple delete the custom step, as the first runnings of 1.090+ grain bills don't need additional water.
Sorry for the book, too much homebrew