Ick! What a awful job. I admit, if it was me, I'd try to think of another way to do it (but probably only AFTER it was all done and I was showering).

I wonder if you could suck up the wheat in a vacuum cleaner and then reverse-blow it into the bucket... or punch a hole in the side of the sack (if they aren't meant for reuse) and fill buckets as it pours out. Or just have a smaller bucket to go into the sack to fill up the larger buckets to be passed on...I'd probably go with the last option.

Actually, if it was me, I probably wouldn't dare that much exposure to wheat. Some people with my problem get sick just from touching wheat.