I have to try your method. Maybe I can get my pattern flying without
'thinking' at all. Right now it is semi-smooth but completely not
mindless.

In a Warrior-II, 152 or 172P with just an instructor and a student, setting
2100 RPM on downwind, and trimming for hands off flight seems to set the
airplane up for a normal approach speed when using 20-deg of flaps, and the
short-field approach speed with 30-deg of flaps.

Are you sure about the RPM? The method I've been taught is
drop the RPM to 1600-1700 (weight depending) when abeam the
numbers and throw in one notch flaps and pitch for 90 KIAS.
On base, 2 notches of flaps and pitch for 80 KIAS
and on final 3 notches and pitch for 70 KIAS. At 2100 RPM,
I'd still a few hundred feet off the ground.

Gerald