Hope you hear from someone who knows what exactly they're using at your lake. I know some anglers sink an old hay bale or a burlap sack with a grain product of some kind to attract baitfish and, in turn, crappie. I used to buy a small bag of pellets that I believe was labeled "Crappie Chum" at a tackleshop but haven't seen any for a long time. Have also heard of fishermen keeping a cage of minnows down in a brush pile but don't know if that was very effective.