I know this is not chumming, and I agree it can be messy. But fish are very nosey! 40+ yrs ago the trick was to take a white coffee cup on a string, drop it to the bottom and bang it a couple times, the white was an attractor and this used to work, no fish finders, or gps, just out where you thought you were in the right area. Most guys I know just use a light mushroom anchor or coffee can filled with cement to bang the bottom and they catch a lot of fish doing that. Fish stop biting, bang the bottom to stir mud and bring them back in. Some guys save their hardboiled egg shells and drop them to the bottom as they fall slowly, white and attract from a distance. Also frozen corn has worked well at times.