To preface, I am not an instructor, and do not claim to have familiararity with training techniques. If pure training technique is the objective, mine may not be the best answer. However, in respect of electric flap aircraft (it's probably not an issue for manual flap aircraft) ...
If you have decided to go after your touch, and you're making that happen, the longer duration and distance you're spending on the runway, the more chance of a problem. Get going, and get back up. Toward that end, acceleration is your priority, get the power on. Yes, with full flap, the plane could get airborne right then, so be it! It could also, if take off flap were carefully set, and you were hit by a healthy gust. In either case, your duty is to maintain control of the plane, your duty is not so much to ride along up again in a prefectly configered and trimmed plane. If you can, great, but if not, you still have to fly it.
All certified aircraft have demonstrated three things in this regard. First, control forces will not become so great, that the pilot cannot maintain control. Secondly, the aircraft will fly, and climb away, regardless of the flap setting. Once climbing away, the flaps can be retraced all the way, and control and a climb maintained, without requiring unusual pilot skill. These are certification requirements.
If in an electric flap aircraft, you select from full to take off flap, and then wait and watch for that setting to be achieved while rolling along the runway at idle power, you're wasting runway, and allowing a hazardous distraction while on the runway. At least in the air, you have only to prevent landing again, of hitting obsticles, while you get the plane sorted.
A part of what is being discussed here is flying technique, but another part is decision making, and the background thinking....