How do you make oleander form a "three-fork, nine-top" crown?

Oleander has whorled leaves in threes and is a typical three-fork brancher, meaning that after each pruning, 3 new shoots grow from the stem nodes. People can take advantage of this branching trait to prune and shape it so that it becomes a "three-fork, nine-top" plant.

When the main trunk grows to a certain height, pinch off the top, and 3 main branches will grow from the main trunk. When the main branches grow to about 20 cm or more, keep 20 cm on each and pinch off the tops again to make them sprout new shoots. On each main branch, keep another 3 branches, keep 20 cm to 30 cm on each branch, and cut off all the upper branches.

After such pruning, a "three-fork, nine-top" crown is formed. If it is not pruned for many years, the branches grow very thin, the old leaves fall off, the lower part becomes bare, and the flowers and leaves are all concentrated at a very high top. The tree shape is then very unattractive, with few flowers and sparse leaves, which affects the ornamental effect.