McLube 1725L Lubricant
Clean thoroughly first. Very, very thoroughly. Masking does not hurt either and it certainly should not touch backchecks.
Outdoors or with mask--particularly with an installed damper section as it "flies back" a bit nasty. Nothing particularly harmful but it's very tiny stuff and never good to breathe.
Perfect dry lubrication for all moving piano action parts. Will not harm wood, felt, leather, or metal surfaces. You gotta take the action outside because it is toxic strong. I’d advise you to wear a respirator. Once it’s applied, I’m guessing you’re good for thousands of friction free repetitions. I hear it comes in non-aerosol as well. That may be the way to go.
