Be in trim all the time...except
Throughout the pattern the student or any pilot should have the aircraft in proper trim (elevator/stab). One should be able to release the controls having the plane maintain speed and attitude.
I allow a bank up to 30 degrees from downwind to base and 15 degrees from base to final.
Once the plane is in trim on final, no application of trim to make the flare should be done...here is where the muscles can actually feedback speed info to the pilot...the heavier the yoke the slower you are going towards touchdown speed (vref minus 5 or so...down to a full stall landing).
Trimming into the flare might give you a grease job once in awhile but you are not ''feeling'' the speed as outlined above. This is for all planes, not just small GA stuff.
and Gosh I hate the C150/52. Much prefer piper cherokees and even the tomahawk. Better visiblity!