Good ideas above. You can get some active dry yeast, the kind used in making bread and other things. Just pour a packet into your 5 gallon can of water and grain and stir it up. This should help speed it up. No substitute for a few good warm days in the sun though.
I usually make 4-5 five gallon buckets at a time. When my supply gets down to a couple of buckets, make 2-3 more. A bag of maize will make 4-5 buckets of chum in water.