Art...I'll assume you have the shoes in their correct positions primary/secondary, that the master is a dual tandem drum/drum master, and the system is properly bleed, and that all 4 wheels are properly adjusted, when you adjusted the brakes manually, did you occassional step on the brake pedal to "center" the shoes in the drum?....if not try that

I have seen conditions where the shoes are initially contacting only the outer edge of the shoes lining, because either the drums aren't cut deep enough in depth to fit the shoes, or the shoes have the friction material installed/overlapping too close to the edge...which can result in erratic pedal/braking issues.....you need to "read" what the surface/wear condition is on the shoes/drums to either isolate it to a wheel(s) before going off in to searching for other causes

Mike