Neatsfoot Oil.

1) get it from an equestrian centre, it pongs less.

2) someone thinks it loosens the skin, mine tightens a day after - so it probably depends on the skin.

3) Put it on the inside where it will roughen the surface and leave the outside alone for smoothness.

4) What do you call 6 bodhran players? Anything you want they can't hear you!