Not knowing how things are hooked up in your car because of what may have been done in the past. Generally a stock car wired as original would have line voltage at the wire from the amp meter to cutout at all times.
https://www.mtfca.com/phpBB3/viewtopic.php?f=2&t=19657
There is a bit more to the Model T generator then just taking it apart and cleaning and even taking it to a shop may not get you up and running right unless they do Model T generators.
While Model T, A and early V8's are three brush types, the T is setup differently.
As stevests said the brush could be shorted, not wired correct inside or could have a bad armature. You might start by taking it apart again and getting the armature check at a good auto parts store.