> How do they get the bags out there?
I expect that as long as the bags are kept off the centerline at the outset, and are kept out of the water as the boat heels, that they swing out there by themselves as the halyard is cranked up.
Think about the bags hanging just over the side, like a fender, but not touching the water. The boat will list a little towards them, right? Any additional random movement of the boat will cause the bags to sway a bit further from the centerline, away from the boat. Once they move a little, just like what happens in a dinghy when you hike to low side, they will be increasing the capsizing force downward on the mast and the boat will list a bit more. As long as the halyard is cranked so that the bags don't hit the water (reducing their ability to pull the mast down), the sway-and-list process will continue with the keel becoming more and more horizontal to offset the bags' downward pull.
Another way to think about it: imagine what would happen if the bags were hoisted to the top of the mast. They're heavy enough that the boat would capsize. But, once capsized, as the halyard was being paid out, the boat would right itself. If the halyard were paid out slowly, the boat would gradually right itself with the bags dangling far away from the hull as is in the picture, and then coming back in alongside the hull.