Hi,
All the listed methods will work when cleaning cork but go easy with the metho if you go that route. Thorough scrubbing with soapy water is my choice but sometimes they need a little more ie.
fine sanding or metho. Applying some wax after you've cleaned them is highly recommended. Don't bother with candle wax or hard blocks of bees wax though. Spotlight and some other craft shops sell an Australian product called Busy Bee Beeswax. It's quite soft and easy to apply but dries to a hard glossy finish that you can buff down. You can reapply some a couple of times a year. It might sound like a bit of work but you're obviously keen to look after your gear. Seeing the grips on some of Bushy's custom rods in the bream bible gives me the heebie geebies
Cheers,
Rigzz