For grafts that don't leave a large wound (like bark grafting) and that depend on cambium contact (W&T, Wedge, ...) and don't really require much pressure, I like freezer tape. It degrades in the field like masking tape and if you use a single layer it does not need to be removed. Unlike masking tape, it has a waterproof coating that keeps moisture out until the graft heals. I like to use a single layer of Parafilm-M on my scions above the graft. Buds easily break through and it helps keep it from drying out until the graft heals.
Thanks,
jack