Cisco, your application method sounds good. I've personally applied it with a trash pump similar to what you're doing with good results.

I use a five gallon bucket (with plenty of holes in it). Put the intake of the trash pump into the bucket. Then I slowly pour the alum into the bucket allowing it to be mixed with the incoming water. I do this off the dam on the deep end and spray in that area. The trick is to watch the PH and apply it slowly.