@dannythemanny I may not have an all-in-one though can see parallels in my process and equipment that makes a difference to efficiency. These are the biggest factors:
- Mill/crush your own grain
- Stir, stir and stir again.
- Squeeze the bag / sparge plate, or some way to help the extraction of liquid (and sugars) from the grain.
Grain crush and flow seems important,
The main benefit I see in having a thinner mash is to wash out the sugars because they're still trapped in the grains. In fact everything else is geared towards extraction - smaller and consistent grain crush promotes the movement of sugars from the grains to the wort, stirring likewise helps wash the grains and promote sugar extraction.
If you have a constant pumped flow through the mash it will be less important to stir, but movement and mixing of the least dense with the most dense wort to is important to promote extraction. Pockets of dense wort in the mash will suffer lower extraction. Clumps of sticky grain or dough balls won't allow flow through so you need to break them up by stirring.
But I think I might be missing something... I do buy grain pre-crushed, so maybe I should buy a mill and go from there...? But these discrepancies are present between the different grain bills using grain from the same bag
I'm wondering whether it's wort investing in a mill just to be able to eliminate crush as a factor
Pre-crushed grain may have settled in the bag, so efficiency is unpredictable from one batch to the next. You won't get that problem milling your own.
Do it! I bought one of the cheap Corona style mills over a year ago and it has been the biggest factor in both improving efficiency and improving consistency. Using pre-crushed grain I'd get anywhere from 68%-76%ish. Now I'm consistently at 79%.
What's interesting is that even pre-crushed grain run back though my cheapo mill also increases efficiency and improves consistency.
pour the grain into the basket and then lower that into the strike water
Isn't this the equivalent of under-letting? I've read that under-letting helps reduce dough balls, but you'd have to lower the grain basket really slowly to let the water filter through grain enough to soak the grains without getting dough balls. It should help though.
I press down on the sparge plate before and after sparging
Equivalent to squeezing the bag. It all helps extraction. I imagine it would be difficult to put enough pressure on the grain using a sparge plate, that's a lot of surface area to apply enough pressure on.
Don't give up hope. Try the simple process changes first before resorting to reiterated mashes. Save yourself a lot of hassle by doing the small things that make the biggest difference. I was amazed at the jump in efficiency I got through stirring, even with a simple one stage batch sparge.
If you want to do batch sparge, do a thicker mash around 3L/kg stir every 15 minutes, drain off all the first runnings, squeeze, then batch sparge with plenty of hot water at 75°C for 20-30mins stir every 10 mins. Drain off second runnings and squeeze again. Remove grain from malt pipe, or alternatively pour all wort back through the malt pipe again for a final wash.