If I recall correctly, the suggestion was to weight the top end of the broom handle with something farily light, perhaps taping a few washers at the end.
I thought of trying it at one time, using some sort of bipod and pulling the trigger by a remote control of some sort, string, etc.
Although the theory sounds okay, I am not sure that it wouldn't cause some type of a barrel explosion. I don't think I would use a broom handle/dowell that was too snug in the barrel.