Letter by letter.
At the blog Socon or Bust I saw a post about a woman who had been writing to her local bishop for some years about liturgical abuses at her parish. The bishop, predictably, did nothing.
She wrote to the Congregation for Divine Worship in Rome.
She received a response from Congregation for Divine Worship in Rome.
The Congregation encouraged her to continue to write to the bishop.
I suspect the Congregation has sent an inquiry to the same bishop to determine what gives.
I have posted TIPS for how to write to ecclesiastical authorities about your concerns. HERE.
The least helpful thing you can do is send a letter full of acrimony and very little proof of what you claim is going on.
Read the tips. Really.