I'm not sure I totally get the question (or the goal) but I do a lot of training where instead of luring the dog (food in hand, holding a ball on my shoulder) I'm deliberately showing the dog what they want, putting it where they know it is, and making them do what *I* say first. So with Nikon this would be doing a little teasing/loading him up for the ball, then I drop the ball on the ground and do stuff like heel around it, even walk over it. When I'm satisfied with the intensity and attention I mark and release him to go get the toy.
In the formal retrieves I want fast, powerful retrieves so I'm more careful about how I do things i training. Normally I work on the impulse control (waiting in basic position for the retrieve command) separate from the actual retrieving, so I don't do many retrieves where I throw the dumbbell and then make the dog wait longer or do other stuff before retrieving. I say this because I've never had my dog leave me early in trial but I did have one instance where I had to give him a second retrieve command.
Whatever you do, just be sure to always mix it up and not unintentionally pattern train behaviors or anticipation that you don't want.
Liesje & the K9s
Nikon (GSD) U-CH SG SchH1 KKL T1 FO PA TFE-I FDCh-S CL1-R UJJ U-CA HIT TT CGC, free reign semi-retiree
Coke (All-American), couch warmer extraordinaire
Indy (All-American), flyball star in training
Rainbow Bridge Kenya (GSD) U-CH FO OB1 CL1-R CL1-F RA HIT TDI TT CGC