So what do you guys use to lubricate the leather pump washer?

The one on my floor pump is in need of replacement. Don't want to offend the Cycling Gods by using the wrong lube on a classic pump so I am sure there is some required lube. Phil Woods grease, extra-virgin olive oil, some other exotic ingredient...

Brooks Proofhide has been suggested for years.

I've used grease (whatever comes to hand) for 30+ years. Seems to work OK. :)