I recently purchased a grain mill to improve mash efficiency with my Mash & Boil all in one electric brew kettle. Today I am brewing a double IPA with about 15 lbs of grain and I mashed with 18 quarts then sparged with 10 quarts. There was a steady trickle coming out of the raised grain bed but it took more than 2 hours to reach my target wort level. I set the mill gap at 0.8 mm. My next step will be to experiment with adding rice hulls at the end of mashing and getting them well mixed into the mash. Any other recommendations are welcome and appreciated.