irby,
I would recommend the type of graft i use to change varieties in trees with 4-5 years + that have a trunk or branches with a certain diameter.
I’m talking of Bark or Rind grafting. If you search on youtube you will find lots of videos demonstrating this grafting technique, like these 2:
https://www.youtube.com/watch?v=LrE2CkQHudI
https://www.youtube.com/watch?v=ZoUrM_ZXoOE
I use a similar technique, just don’t like to use too long and skinny big scions like in the videos (3 buds max). I also prefer to graft only 1 or 2 scions if the diameter of the trunk/branch is not very big like you can see in the above photos. you can also leave a couple of branches of the original tree in the first weeks after grafting to help move the sap.
Here’s another example. It’s a wild apple from seedling that i grafted with Granny Smith about 3 years ago.
The tree in May of last year:
I now decided to cut the 5 main branches that where growing from the 2 original grafts and turn this single Granny Smith in a 5 variety tree.I left one branch of Granny Smith that i probably won’t cut totally because this variety is a good pollinator.
The new grafts in May:
The grafts in July:
I will try to post an updated photo of the “new” tree…