Um... well... kinda on the fly... We had had steak that night, so I saved the bones, and the fat trimmings. I cut the fat trimmings up really tiny, and took her off away from the other dogs for some one-on-one time.
I took some paper cups, and a peppermint and a cammomile tea bag (the cammomile ended up confusing her, so I tossed it). I started by putting the tea bag and the treat in one hand, and waiting for her to "attack" that hand. Then I would open it and reward her. I also used the paper cups on the floor and had her sniff them, treat and tea bag in one, other scent in the other one. She would get the treat only if she found the reward. I can't remember EXACTLY how I did it, but I'm sure you could find lots of educational videos on youtube.
I eventually got her obsessed with that squeaky tennis ball by rewarding her for working (she actually LOVES to work, and is verrrry driven, so not all dogs may learn so fast or with the same methods). Then I stuck the tennis ball in a tuppaware container with the mint tea bags. Sometimes I would hide the sealed container, sometimes the scented ball, she always found it. Regardless, I always give her the ball when she finds the scent... Sorry I'm so confusing! It's hard to explain how I did this...