Before the Inter 20 North Americans in Connecticut several years back, one skipper was using a new crew for the regatta. When the other I20's were doing a practice race, this skipper took his crew out and did 200 tacks and 200 gybes to practice. He ended up winning every race and the crew said that the practice they did helped enourmously. They came out of every tack and every gybe with an advantage over their competitors which made that team dominant. I don't know how much it would help your Tybee race though.

Mary is right, the drills I learned in Rick White's Sailing Seminars (I have attended 2) are terrific for getting things right for going around the bouys. They improved my performance on the water. My suggestion is an additional alternative, not suggested as a replacement for what Mary told you. BTW, if you can get your team to one of Rick's seminars, you won't regret it!