I know all about burrs. I have ruined a few things over the years. Like a $80,000 coupling for a shaft.
Coupling was a interference fit. Meaning the bore of the coupling was smaller then the diameter of the shaft it was going on. Shaft diameter 12.000". Bore diameter 11.980", 0.020" smaller. Have to heat the coupling up to expand the bore diameter. Heat it 600F to grow the bore to 12.010". Start to slide the coupling over the shaft. Coupling started to cool off. Picked up a burr about 90% of the way on. Stop the coupling dead in it's tracks. Hurried up and threw more heat to the coupling with 3 rose bud torches. Stuck! End up machining off the coupling and ordering a new coupling.
What saved my bacon on that job. I had the foreman right there with me, giving me a hand.
What makes the diff bushing install hard is that it just like the above, but without the heat. And the sub-frame hole is not perfectly round either. It's somewhat egg shaped from the welding on the sub-frame.