Going through private pilot training, I was taught to trim the airplane for all phases of flight. After fighting the controls for one too many flights, the lesson took. Like most students, I was also told to trim the airplane for steep turns. Although trim makes the turn much easier, I suggest that you try steep turns without adjusting the trim wheel.
The tricky thing about steep turns is not the steep turn itself. In fact, once the proper pitch and bank angle have been attained, you only need to hold the controls steady while making minor corrections.
Most pilots mess up the steep turn at the entry or completion of the maneuver. They either start out with too much or too little pitch. This isn’t a serious problem, and it tends to work itself out with experience. At the end of a steep turn, pilots tend to climb well above entry altitude. In most cases the culprit is the trim.
You see, by trimming the airplane for a steep turn, you are actually trimming for a nose-high attitude. Once the wings are level, you have to fight the airplane to maintain level pitch-attitude until the trim can be taken out.
Pilots should not trim for steep turns. The maneuver becomes much simpler: Roll in and stick the nose in the right spot. Hold the controls steady. Roll out on heading and pitch level.
Since the airplane was trimmed for level cruise flight before the maneuver, the airplane ought to settle in to level cruise quite comfortably at the completion of your steep turns.