Stick the brass bushing inside the freezer for 15 min. The brass will contract in size . Then Heat up the Spur with a Heat gun or hair dryer. The Spur will expand. So it is very hot to the touch, use gloves to handle it. Then quickly insert the brass bushing right out of the freezer. Should fit in/ slide in easily enough. Try that. As both metals get to room temps, the bushing should become nice and snug.
Let us know how it works out.
I would imagine the brass bushing in this application
should be a very tight fit for best operation.
Brass Oilite bushings are soft. I would Not hammer it.

And No need to.
My 2 cents.