As for cleaning silencer, you'll have to follow Charles's advice, but you can't do this on the NSR cans unless you chop them apart.
Expansion chamber cleaning advice using the wire is the best plan and gets rid of most of the carbon built up, but I'd recommend taking the bike for a good hard ride before hand to try and burn off/dry up and goo that's hiding in there or it can get quite messy.
Oh and Charles, how dare you say that we just throw the silencer packing straight in the trash here in Thailand. We always wrap it up carefully in a 7-11 bag first, and then throw it in the trash
