Nugget's Dad - it's not really my place to say anything since you've done all this before and I'm just learning...
But one thing I was thinking about that helped with my Jacks was really cracking down on the impulse control even before we got to the level in training that we are at right now.
I used things that definitely motivated him - toys and treats. Even working in our basement, putting 1-4 toys out around us and directing him to retrieve specific toys - even when there was a high value toy (his favorite ones) out there. It's helped in that while doing the glove exercise at class for the first time, my only real concern or "must work on this" was doing a clean pivot and remembering that once you stop moving your feet you can't readjust yourself. Well that and getting him to just retrieve the glove without shaking it around. This went into the dumbbell retrieves as well, where we are basically doing a directed retrieve where the dog is looking at two dumbbells and must retrieve the correct one.
Using the toys and training in an informal way also took a lot of stress out of the equation for the dog - which was huge for Jacks who "stresses up" and tries his hardest when I'm teaching him anything new.
Adele also has had us set out multiple targets (paper plates or her rubber circles) and load them with a treat. This trains the directed send and impulse control well before you add the retrieve to the equation. We'd have 2 circles out there and start off only loading the one. She suggested adding a treat to the other when the dog isn't looking, but that was NEVER going to happen with Jacks who moves faster than the speed of lightning when food is involved.
So I just would send him to a treat and call him to come to a treat in hand before he had a chance to break for the other treat. Again this went into training the directed retrieves before the gloves got involved.
The go-outs too, I was having a problem with Jacks not understand the go-out exercise even with a treat out there, my instructor had me stand practically a foot away from the target with Jacks and either load it or give him a job to do and gradually backing up a foot at a time.