I just used mine to plant beans this weekend, had the same problem you did. I found out that if I slowed waaay down, to maybe 3 mph, population would come up to where the transmission was set. Otherwise I was planting at 5.5 mph, I couldn't bring myself to plant the whole field that slow. I decided that the beans simply couldn't fall into the meter fast enough. Mine were 2800 seeds/lb, with the meters on the "B" setting, per the book.

Next time, I will try the washer trick. Sounds like a good one.