what part of the brake is the bushing? and how would you make it thinner?
the part that is directly in contact with the frame boss.. front to back thickness of the brake
how skilled are you with a File? know 1 type from another?
sanding reduces the boss diameter, not altering , the length.
grease only the outside of the frame boss
The cleaning the grease and oil off, inside, thread lock app on the bolt
is probably the easiest to explain over the web.
sorry i got to that last..
instead of son of a machinist options, I've used before..