Muscadines are difficult to graft. It can be done, though. The best success I have heard people have is with approach grafting. I would just buy 2 vines and plant them in the same hole. Each vine can become an arm. You will get the same effect with a lot less work. The vines ground layer incredibly easily, by the way. If you bury part of the vine in moist sand it will naturally form roots in just a few weeks during the summer.