Lisa, I understand how physical limitations restrict what you can do but, here's a suggestion. Since you have access to a dump trailer how about trying to bag your own at home at your own pace. One could place a piece of plywood with a hole or slot cut in the trailer before it's loaded. The hole would restrict and control where the coal flows out of the trailer when you raise it. Place your own bags at the opening and fill them to a weight and volume you can deal with. I get free re-enforced plastic bags from various farmer sources. I got my latest supply via my local freecycling (http://www.freecycle.org/) group. They had contained chicken feed.
When I go to the breaker I get my trailer slightly overfilled. Then after I'm weighted I bag and transfer some of the coal to my pickup bed to reduce the weight in the trailer and increase the weight in the pickup bed. The truck rides much better that way. I use the bagging technique described here: Self-bagging Coal
