I really like the 9122 drives in terms of reliability (of both drives and media). I've had excellent luck restoring them - I've been through a half-dozen or so and all except one have been fine once the drives are freed up (the only failure had obviously been flooded and the drives were corroded and rusty).
I use spray contact cleaner to dissolve and then flush out the old lube. The most gummed-up part is usually the large flat plate on the right side of the drive (viewed from the front). It's just a matter of applying solvent, letting things sit for a little while and then starting to wiggle things as they loosen. As long as you're patient and don't force anything, I expect you'll be successful. There is probably no need to apply lubrication after cleaning since (1) there is probably a little residual lube and (2) you're unlikely to subject the drive to heavy use once you've restored it. If you do want to lubricate the moving parts, I'd consider a minimal amount of Nye synthetic clock oil.
I also very carefully clean the heads with alcohol on a swab while the drive is removed from the chassis. If you have problems with a single drive, you can also swap their positions - I think there is a small switch on the back of the drive to set it for 0 or 1; my memory isn't clear on this, so check the manual.