When you get the trunk to the size and taper you want, then you will begin making branches, and not before. What is true of all bonsai is especially true of prunus mume: you can work on the trunk or the branches, but not both at the same time. Working on branches and keeping them in proportion requires that the tree be grown in a pot. They get too big and can't be wired properly in the ground.

Please forgive me, I am quoting from memory, but I did reread this article yesterday.

Quoting from International Bonsai Magazine, 1982, NO.1, P5, Tomigoro Komaki:
"The plants are dug in early spring, prior to growth, and trimmed. Heavy roots and smaller ones appearing above the root system are eliminated. The large heavy roots are cut back to about one-half inch. It is important that all roots are trimmed to this lenth. Roots developing downwards from the trunk and others growing downward from the radiating roots are also trimmed to allow the plant to sit flat.
The trunk is cut back to about one inch above the root system, retaining two buds. The cut is made on and angle with the upper bud on the outside. The wound will be large, but this is not important at this stage of development." (Emphasis added).

For the next few years you will remove all the branches by cutting horizontally. Don't carve the wounds until later.

Please realize that I am quoting from another author's work, and I have never developed prunus mume using this or any other method. However, it's a good, scholarly article that I believe shows an excellent way to produce massive taper on mume in a short amount of time.