In this paper a multi-user virtual training system concept for force skill training is presented. A trainer and a student connect to a common virtual environment via their individual haptic displays. The student realizes the virtual task, while the trainer observes him/her visually, acoustically and/or haptically. The trainer has a chance to correct the student verbally or haptically. Alternatively, the observation duty is given to the student, while the trainer demonstrates a task. Depending on the combinations of these observation/correction possibilities, three novel training strategies have been developed. Force information is exchanged on a separate communication line, which minimizes the time delay. The efficiency of the developed training strategies is verified via user tests on the bone drilling medical training system that was developed in our laboratories previously. Last, but not least, a special attention is paid to objective assessment of the user tests' results. Thus, a method based on distances in n dimensional Euclidean space is developed and implemented.