Hey @qpola I too have been having my own growing pains with Multires. There are some bugs and quirks with it I am finding. All in all I am glad you worked around your issues.
There is always the masking tools in sculpt mode that can help keep certain parts of the mesh stable while also sculpting details. There are also some very unique line trim and other tools on the bottom of the brushes toolbard that may help flatten things that are looking mushy.
I even used the SCALE brush to accentuate some of my details in a direction (Z direction in my case) and then I used a combination of mask and the LINE PROJECT to cut things flat again.
Not sure if those will help or not but I’ll be available some evenings on discord this week if you’d like to stream and brainstorm.
