Hi Francis, yes it is that simple. Find a suitable branch that you want to use as a scion. Make sure it has at least 3 dormant buds. Then cut several inches below the lowest bud.
Find a drill bit that is just about the same diameter. Drill into the trunk where you want the scion to go.
Here is the important part. The larger the scion the deeper the hole. So I placed my scions into the trunks about 4 inches deep. I know the scion needs to self support itself so the deeper insert regulations that. Then strip the bark from the scion as deep as the hole is in the trunk. Try putting some nail polish or paint at the 4 inch point on the drill and this will help for depth consistency and lining up the cambrian of the trunk to the scion.
Then simply and gently tap the scion into the hole in the trunk.
Stop tapping when the cambrian no longer is visible.
Spray the scion and the trunk around the area of penetration..
As a alternative I also took rooting hormone on ½ off the scions and simply drove them in with the powder on it.
As of today I see no benefit...yet.
You will find some of your drilled holes too narrow so if they don't go in easily with gentle taps stop, remove the scion and drill it again but wobble the drill bit slightly.
Just a technique that I am sure you will improve on.
Ps the paint is a spray on tree pruning sealer.