Damping of bottoming-out noise is pretty much solved: O-rings of the right thickness or "trampoline mod"
Damping of topping-up noise: Liquid latex has been brushed on the top of the inside of Cherry MX housing.
But I think it would be hard to get the result consistent. I suppose you could use silicone rubber instead. I would be wary about using silicone caulk though — because that releases acid when it dries.
The best silencing mod for Cherry MX is to use QMX silencing clips, but the keyboard needs to be built just the right way.
"Silent" switches are still better though.
Read more on
Damping in the Deskthority Wiki.