Rent one of those gasoline powered waste pumps. $50 per day up here. We used one with a 2 inch line to put 4000 lbs of lime on my pond this year. Just pour the gypsum in the water in a small pile near the shore line and then slowly shovel the gypsum toward the intake hose. It's a 2 man job. Took us about 1 1/2 hours to distribute 4000 of lime. Reduce the output end with a 1 inch or 3/4 line and you will spray the gypsum laced water a long way.