Forgot to post my post-mortem. Wound up hitting very close to my intended gravity (1.090 of 1.093), which is the best I've ever done for an all-grain beer this size. It was a huge grain bill, too: 22.2 lbs of grain and 6.8ish gallons of water in a 10-gallon MLT made for less than 2 inches of head space, barely enough to screw the cooler's lid on!
I forgot to collect my mid-lauter SG, so I couldn't fill out Kai's entire spreadsheet, but it's good to know I could have. Unsurprisingly, my 60% estimate of brewhouse efficiency wasn't far off: with that much grain it's just hard to lauter well.
Calibrated and used my refractometer for the first time, and learned to convert from Brix to SG. Great to be able to get a quickie gravity reading without risking my hydrometer in hot liquid.
The dipstick did its job. I marked it in quart increments, and it's awesome to know I don't need to guess at volumes any more!
Thanks again to everyone who pitched in on this thread.