Nautilus cleaning

[Rider]

Thanks Paul.  I understand about the bouyancy and the chambers.  Unfortunately the first chamber on mine was filled with rank seawater, perhaps from long exposure to wave action.  The second chamber seems dry.  In the absence of other information, I bit the bullet and drilled a small hole next to the valve to allow some equalization and permit water to drain out.  Having done this I inadvertently discovered it helps to leave the shell in the sun.  The heat build up inside the chamber seems to have helped push moisture/vapour out of the hole I drilled.
I'm afraid I also bit the bullet and ended up using a mild bleach solution (1/4 strength) which has helped remove most of the (what I take to be) periostracum (black stuff).  The pearly part still seems pearly but I hope I haven't degraded it.  Is it possible to polish the shell up?  If so, what would you recommend?
Cheers
Phil