In the past I’ve used one of those 11lb Esacli scales for weighing out grain. It works well enough but the size of your container is limited by its plate so I only ever could weigh 4 pounds at a time. While getting a bunch of other cheap junk to play with from DealExtreme I picked up a hanging scale. It hangs from my basement ceiling and works very nicely for weighing out grain. Tare the bucket, dump in the required amount of one grain, tare, dump in the next, etc.
Ideally I’d have a plate scale that could handle 30+ pounds but this was a much cheaper alternative1