If bush beans are like bush snow peas, you could run one (or two) string(s) between two stakes,about 8-12 inches above the ground.
Tie it to one stake, then kind of thread it "through" the prostrate mass of bush vines, and lift the up as you tie it to the other pole.
When I give them even one string BEFORE planting, they grab it and have enough support to stay off the ground. My bush snow peas (24-36" vines) seem MUCH happier, get more sun, and are easier to pick if I give them 1-2 horizontal strings, say at 5" and 12". Otherwise they sprawl flat on the ground.
