Pull the power when turning base.

[Silvaire]

Not really correct without qualification. It works that way if you're trying to maintain a fixed vertical speed, which is indeed the usual scenario. But you can trade airspeed for descent without adding power.

And the transition is rather broad; it's not a "specific" point.

I'm not sure what you mean by "broad". For any individual configuration there is a specific point were you cross over. Also we are not talking about descents since a descent is not sustainable, eventually you will contact the ground.