I like the HTH from Wally's the best. I usually put 2 lbs in a knee high stocking, in front of a return. I tie a string to the stocking and wrap that around a rock. A couple of bricks will work, also. Sometimes, if I get it just right, I don't have to readjust the stocking, in front of return. The HTH, being almost a "powder" leaves the stocking much faster than others; even faster if you massage the stocking some. In front of my fastest return almost 2 lbs will be gone in a few hours, even if I don't massage the stocking, very important if you have pets that might play with it. The warmer the water the faster it disperses. I know this because I keep my pool open year round, and have to replace CYA pretty frequently due to frequent backwashing. I do have "dust bowl" conditions year round.
gg=alice