For a quick repair of a loose flapping buckskin on the hammer butt, would contact cement be a good glue to use? Is there something better out there that might be easier to remove in the future if needed?
Tunerjoe
Paw Paw WV.

I would probably use wood glue (yellow glue). It dries fairly quickly and is easy to undo if necessary.

I was concerned with the glue soaking into the buckskin and for an in house repair I would need a way to hold it in place while it dries. Maybe a small ball of scrunched up paper wedged in there to hold it in place. The bottom is still glued but the top wants to curl away from the curve on the butt.
Tunerjoe
Paw Paw WV

For that repair Joe, I stuff the tip of a wedge shaped wire mute in between the jack and the butt. This holds the buckskin in place while you tune the rest of the piano.