Many would contend that it (DA/SA transition) IS difficult to master.
That could really only be true of those too cheap to buy some snap caps and too lazy to practice dry firing for familiarization.
First dry firing DA, learn your trigger reset.
Second pull, thumb the hammer back and dry fire SA, learn the SA trigger reset.
Repeat as necessary until it is second nature, just like any other training.
A DA/SA trigger is self-consistent. The transition between modes is predictable, always occurs in the same sequence while firing, and it is not difficult to master.