Likewise, I use small square nuts commonly used in fencing, 100 of them, I count them in and then count them out, fishing them out with a telescopic magnet, as you are only really concerned with the sludge on the bottom I work on that predominately, and if you have left the headstock in place it is better than any Bullworker and a lot cheaper then joining a Gym. I did think about using the cement mixer method, but I reckoned that even on the slowest speed the nuts would centrifuge into one place and achieve very little, so I made my own crude device with a crank handle a few pieces of metal and a lump of wood, now I can clamp my device into a Workmate bench, attach the UFM to it with small ratchet straps and swish away in either direction to my hearts content, it seems to work a treat and looks squeaky clean inside, I have done a few and never had a problem afterwards.You hear horror stories about cleaning out oil tanks, but I've had good results cleaning all the ones I've done........The worst one was probably the one on the twin racer, in my pic on the left......It had a layer of thick sludge on the bottom........Soaked it in good degreaser and a hand full of sharp edged 1/2" BSF nuts, worked it back and fourth over a few days, then flushed it many times with clean petrol, and it came up nice and clean........No problem.