Ok, so the mashtun worked AMAZINGLY well last night. I prefilled it in the tub with hot water (≈ 120°F) and dumped it out (probably a little too early, about 30 mins) before adding the strike water, which was 10.5 gallons of 185°F, campden-tablet treated, filtered water. I overshot the strike temp on purpose, and we did have to add some ice to cool it down to 160°F.
I mashed in the the grist just a little early cause I didn't know it would hold the temp so well - at 163°F, putting my mash at 151°F. We assumed it would drop to 149°F but it never did! Stayed at 151°F for the whole hour. Awesome, except I wished we had waited until it was exactly 160°F so it would've been at 149°F but 151 is fine.
After vorlaufing a few gallons of water, we iodine/starch tested a sample. No black, all converted! We collected ≈5 gallons and then added ≈3 gallons of sparge water (180°F), let it sit 10 mins but it still looked too thick, so I added the rest of it for 1 batch sparge. It worked well, we hit 1.076, which was way higher than the predicted 1.055. This was based on a Refractometer Brix Reading of 18.5 @ 145°F.
Side question: does the refractometer need to be adjusted according to the temp?
The boil was kind of rough. It was cold outside and it wouldn't stay rolling unless we put a lid on top of the kettle, allowing just a little steam to escape, not to mention the fact that it took a good hour to get it to boil. Yeesh.
Moving to the fermenters was kind of rough, too - we used a funnel with a filter at first but we could only pour so much before it got clogged with hops. So, we just poured it the two carboys, hops and all. So much foaming when we poured that it was coming out of the top! Then added the yeast, I'm eager to see how they're doing right now when I go home for lunch...
Thanks for all the help guys, I think this brew might actually turn out great! I'm gonna let it sit for 3 weeks, then possibly dry hop for 2 or 3 more in a secondary, then let it sit in my corny keg for another 2 or 3 weeks before I force carbonate.
Again, does anyone know if you need to calibrate a Refractometer based on the temp of the wort?