... Rather than pulleys, I have found a simple cheap tie down lashing strap works very well, tie it around the top of the bag w/ the clamp close by.
http://www.harborfreight.com/automo...of-2-1-inch-x-12-ft-lashing-straps-67386.html
I just slowly lift and cinch tighten the tie down strap as the bag comes up...the benefit is that the strap locks and takes the weight, lift a few more inches and let the bag drain...when done draining have a large bucket to lower the grain into.
below is another example, but these straps are more complicated to use but will easilly lift 1-200 lbs...
http://www.harborfreight.com/automo...ch-x-15-ft-ratcheting-tie-down-set-90984.html
The benefit of these types of straps is that they lock and take the weight for you. With the ratcheting strap, grandma could hoist 100 lbs easily.