I wash them with regular tap water or sometimes RO water (if tab water is too hard). I use a good shampoo or hand wash fluid. After washing, I wipe with a banyan/Vest (I buy them and never wear them) and finally with kitchen paper towel.
For really adamant dirt, I use Fevicol wood glue, apply uniformly, let it dry and finally peel off the skin.
The above two have given me satisfying results but there are a couple of records that never got fixed!!