I have already started grafting green on green, this type of grafting works if you graft the wood same day you harvest. Give it a shot.
Thanks to the heater failure I replaced lost stock green on green, against the advise of a few. Have done at least 50 grafts on citrus, cherimoya, mangos and avocados and now have a greenhouse pretty damn full of choice stock.
Green on green was not by choice but by necessity. Even the new triangular citrus shoots back in March worked. I converted some of the branches of a large key lime tree with 4 orange varieties, limequat, & Persian lime. You can do it but have to be especially careful to get a good cambium match. I choose between side veneer, cleft, t-bud and bark grafts depending on the situation. The cherimoya had 2 veneer and 4 cleft. All took.