I find this topic very interesting. Feeding the fish, or stimulating them to feed with what we put in the water.
I remember years ago when the "baggin waggler" was being first used at Drayton. The method used very very fine fishmeal groundbait around the feeder. The only thing edible for the Carp to actually eat was the hookbait. The fish would smell the fishmeal dropping off the waggler and then sift through the fine G/B coming off the feeder but not being able to feed off the G/B and eventually come across the hookbait and go for that.
Groundbait being thrown in at the start of a match. Loads of balls of G/B but maybe not a lot of feed content in them. More of a carrier of freebies than food. Leam used to enable Bloodworm to sit over it rather than burrow into the bottom. Double leam, one for the Bloodworm to sit over, the other as a binder to enable the ball to be thrown in. Emptying a G/B feeder mid water to let the particles drift downwards rather than in a pile on the bottom. All to stimulate fish to feed.