1) Just look up "chemical supply" in your area and make a few calls. I got mine from Estes in North Dallas.
2) Start off cautious, monitor your PH levels, you will see results overnight. I originally bought eight bags (40 or 50 lbs each). For the first application I used 2 for my initial dose for a 2.5 AC pond.
3) I simply paddled around in a jon boat, mixing pond water & alum in a 5 gal bucket, then dumping it overboard, I'm sure there are easier ways.
4) I did NOT want to kill my fish like Terry Bradshaws ! I had time and applied smaller doses. It works very fast.
5) My pond stayed clear after the initial treatment. It always went somewhat muddy after a big rain event, so I stacked the remaining bags I had on a small gully that fed into one of the creek channels I had for runoff. They lasted about 2 years before it was all gone.