David,
Everyone has his or her own way of handling something like this, but I believe I would take dormant budwood, of the variety you want to put on the rootstock, around the first to the middle of February and hold it in the frig. I would fertilize the rootstock good in February and get it into shape to make a good flush of growth in the spring. Then bark graft the scions to the rootstock on the first flush. You will get better results just as fast as cleft grafting now.
Ned