I do not grow muscadines as I live in SE WI. I do have the same issue each year on my early ripening grapes such as Reliance. With no control, I lost 80% of my crop.

I resort to using wasp traps that I purchased at our local
fleet farm store. I fill them with Mountain Dew soda and hang them around the ripening grapes. I have to empty and re-fill the traps every two days. I still get damage but I would guess my problem is 80% reduced as long as I keep the traps emptied out.

It seems once I get the first few wasps in the traps, they fill quickly after that. I often wonder if the buzzing attracts more wasps?

For a grape row with 5 vines, I hang out 5-6 traps.

I put paper bags or netted bags around mine and it works very well. Had three bunches of Princess I would not have been able to harvest were it not for the bagging. They still gather on the bagging. I guess the aroma still attracts them.
They also go for the Goji berries, figs and blueberries
I have my blueberries in a greenhouse to solve the wasp issue because, it is impossible to protect them unless you cover the whole bush with insect netting.