I harvested some rhizomes today from a three-year old Cascade plant, so I thought I'd pass on some pictures for those heading down that route in the future. Ended up with 20 large rhizomes and 40 small ones off one plant and left the crown to grow this season. I used the old steak knife in the bottom picture to cut off 6-8" pieces with buds on them.
A couple of observations for new growers: Growing hops in manageable-sized, bottomless planter boxes that you can lift off (so don't anchor them down) makes the process so much easier. I grow mine in half wine barrels that have had the bottom cut out, with the wide end toward the ground. Basically, they're like a circular planter box. Raised beds help with drainage and keep my critters/kids off of them, too. If you can source some scrap wood, or use some cedar fence planks, you could do it on the cheap.
See pictures below. The first picture is what the crown looked like shortly after I lifted off the wine barrel. The second pic is what I left of the crown. The third pic is another planter with some snow peas (hopefully, adding a little nitrogen to the soil for this season) and last is a shot of a few typical rhizomes.