I can confirm that single-infusion works. For best results, use an amylase addition as directed. At Ghostfish we do a 2-hour mash from between 152°F to 158°F, and I honestly can't say that I have noted any major differences. I crush the grain with a 2-roller mill and seem to be getting good results with a .63 mm gap setting. The v-wire on our false bottom is gapped at about .7 mm, but unfortunately (because the screen has to be modular to remove through the manway) the gaps between screen modules exceed 3 mm in places and allow a bit of grain through.
The single most important thing I have learned when mashing with millet is DO NOT FLY SPARGE. The nature of the grain bed is to cause severe channeling of the runoff, even with copious amounts of rice hulls. You just CANNOT get a good rinse of all parts of the grain bed. If you taste the spent grain, it should be completely bland--if you find any sweetness, you left sugars behind and need to tweak your sparge method.
On our first few "big" batches we sparged the way the system was designed--i.e. a slow run-off with the sparge ring keeping 1-2" of water above the grain bed the whole time, and we achieved terrible efficiency compared to what I was getting on my 3-gallon setup where I batch sparged everything. I chalked it up to the bad crush we were getting with the grooved rollers on our mill, but when we installed our 0.5-bbl pilot system, I used the same Monster Mill I've been using for 3-gallon batches for years and got similarly bad efficiency. I decided to try fly sparging on my old 3-gallon setup just to isolate variables, and indeed! Terrible efficiency. So I tried a very tedious underlet-infusion batch sparge technique on the pilot system with LOTS of mixing at each step of the sparge, and wouldn't you know it, I was back at the same kind of efficiency I was accustomed to before!
For the record, for pale millet malt I assume a max system efficiency of 75% and a max theoretical yield of 30 PPG, and I hit my numbers within one or two points almost every single time. It also helps to do smaller batches when batch sparging--3 or 4 instead of 1 or 2. I do use rice hulls because the grain bed is pretty gummy by the 3rd sparge and after one 14-hour day on the pilot system (pre-rice hulls) I vowed never to stick the sparge like that again! I use around 1/7th of a pound of rice hulls for every pound of grain and finally have normal-length brew days again.
As to how it's going to work on the big system, I don't know yet because I'm still waiting on a set of knurled rollers. Grooved rollers at 10 grooves per inch do NOT do the job. But I intend to use a similar method as I do on the pilot--mash, vorlauf, drain, underlet, mix, vorlauf, drain, underlet, mix, vorlauf, drain. It'll be a long brew day, but 70% efficiency vs 15% efficiency makes it very worth it. I'm sure I'll eventually streamline it.
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