Hi Photo, I have found that to do a good POI takes sideways travel along with very precise Rudder or Yaw control. Doing so manually is easy if you practice it enough. As you correctly point out, using the Trim should be advantageous because it automates one of the two necessary functions to perform POI sideways travel with Yaw control.
However I have found that when using the Trim Function, the application of rudder does not effect the craft's travel as it does when doing so manually. It begins to Yaw in the direction desired but the craft continues to travel in the previous direction until; it hits a point of about 15 degrees of yaw and then shoots off in the new direction.
For this reason, the Typhoon H Trim Function (In my opinion) does not allow a good smooth POI Unfortunately.