Death, I'm looking into doing this stovetop AG method but on a smaller 2.5 gallon scale:
Have one question: After mashing in, what do you think will be the difference between
1) transferring the grain bag to a different kettle with 185F sparge water to get the grain to the desired 170F (as you describe), or
2) just adding a few quarts of boiling water directly onto the mash to get it to 170F (step infusion?)
Do you think there will be a difference in efficiency of the extraction?
There is, as the transferring to the new kettle will help rinse the grains of any sugar that didn't make it into the main wort, where as just adding the boiling water will just raise the temperature of the mash.