Brake problem!!

Ok! Here's my problem I'm running a '73 Plymouth Duster with stock drums, and it's been sitting for about 18 years and and towed it to my shop. Before I towed it I made sure the brakes work which they didn't and so I went through and bleeded them, I did this spring of 2011. Today I had it running and took it for a test drive, I noticed that when I hit the brakes only one of the drums would work I'd then attempted to pump the brakes on all of the drums worked! Why does it do this, what could be the problem, and finally what do I need to do to fix this from happening again??