It's the thorough cleaning I'm after.
The rocket blower and sensoklear pen havetill now done a decent enough job, and I think will be ok in future as part of routine maintenance.
But I need something to get the stubborn stuff off and that is going to have to be a wet method.
I'll take a look at their wet system. I was lookng earlier today, If I'm not getting my brands confused they do the "green" swab system. I think it was about £30 for a dozen wipes, then I guess it will bea few more pounds for whatever fluid they make.