Depending on the grievance mechanism, you may have an active role to play in the process. In a dialogue-based, problem-solving process, it may be necessary to agree to the terms of mediation. You could also be asked to provide more information.
Some grievance mechanisms may undertake official fact-finding processes, which could require preparation in advance of the visit such as arranging meetings etc. It may also be necessary to travel to participate in meetings. Some processes can be completed within months. Other can take a year or more, and there are a few that can take many years.