Max,
If it were a truly expensive pipe ($220 and up), you would have been asking
this question long ago. The inside you do not clean. never ever. Use use a
cleaning tool that scrapes the char out. If you use this tool correctly, you do
not remove much each time. If you are too aggressive you will pull clumps out,
leaving no char in that little area and that will allow that spot to burn
through.
On outside, if it is real yucky, you can scrub with toothbrush and very mild
solution of water and murphys oil and wipe clean. When doen, use your noce oil
to add protection. SOmeone already mentioned this. It works and works well. Rub
on your nose and use your fingers to loveingly rub it in. A $200 plus pipe will
retain in value, and smoke well. ANd dont smoke one pipe all the time. It needs
a rest.
None of these rules apply to meerschaum.