Those little brushes on older LGB locos, where the spring and brush are loose, are hard to change. If you’re not careful, the spring tension will throw the brushes across the room when you’re trying to get one on the opposite side. I got tired of chasing springs and brushes, so I made up a little tool out of brass sheet.
This is a sheet of brass bent in a “U” just wider than the space between the loco brush holders. You put the springs and brushes into the holders and then slip this down to hold them in on both sides. Then it’s easier to get the wheels to go down over the brushes without having to fiddle everything around.
It certainly makes it a lot easier to deal with getting the wheels back on. I don’t know if I could have gotten my LGB Mallet back together without the tool–I might still be at it.