Doing a patch-up job on a starter with enough time and wear on it for the drive clutch to start slipping without addressing other normal wear areas like the brushes, bushings, and solenoid linkage is false economy. It takes almost a complete teardown to replace the drive unit. You'll probably be money and time ahead to swap for a good-quality rebuilt starter, or get a new, lifetime warranty unit and make it the last starter you'll ever pay for on this vehicle.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!