Sound deadening materials/coatings for a project.

I've built a couple such mechanisms for medical applications where I had to avoid giving auditory cues as to movement. There are some fairly quiet ball screws (I think Festo has one), but I've also used belt drives, hydraulics and pneumatics. I would initially try for a belt drive, though I understand there are some quiet chains as well.

Call in your sales reps.

Isolation is probably your best bet. I doubt that paint able material will help much beyond making sure the sheet metal does not act as a drum head. Soft mount any attachments between the actuator drive train and the structure, and then if necessary use the paint on material to dampen the structure.

Try marine engine compartment acoustic foam, available from major boat chandlers and specialised sources. It is applied to the inner surfaces of the enclosure within which the noise-generating equipment is located.

Many years ago, the top half of a room was lined with this stuff: the room contained a compressed-air-operated can inversion and blowing machine that registered intermittent levels of 93dBA. Prior to installation the walls and ceiling had hard surfaces that reflected all the sound. Operatives had to use ear defenders in the room, for obvious reasons.

After installation it was down to 86dBA.

If you have a pivoting device, you can use a nylon bushing to isolate noise, vibrations, and harshness.