Twiddling the trim wheel to make glide path corrections may work okay on a C150 or PA28, but remember that that techniques that you are taught are generic and are devised to work for all aircraft types. Try it on a much heavier aircraft, such as a Cessna 210, which has much greater inertia and responds much slower to trim changes, and you'll find yourself oscillating above and below the correct glide path as you try to get the trim right.
Remember the technique: select attitude - hold and wait for the aircraft to respond - trim. If you do this, you'll be able to fly a stable approach in virtually any aircraft type.
Re the method of deliberately setting the trim nose-up for takeoff, I think that this is a rather bad idea. As soon as the aircraft leaves the runway, it will be in ground effect and will start to climb steeply. Once out of ground effect, the rate of descent and the speed will drop sharply - not a very good position to be in! Set the trim to the recommended takeoff position and use pressure against the trim for transient pitch changes where necessary.
Some aircraft types that I have flown actually need forward pressure on the stick against the trim when you leave the ground to allow you to pick up speed before climbing out of ground effect. If you fly a tailwheel type, you'll need to hold the stick quite a long way forward at the start of the takeoff run in order to raise the tail. You then start to apply gentle back pressure to hold the attitude and gently increase the angle of attack. You couldn't do this in a controlled fashion with the trim wound back - generic techniques again!