Hey bud,
Keep it simple, if it's mark and or even a dozen marks on your hand from the permant marker, just rinse off if anything I wouldn't even wash with soap because the soap residue will probably do more damage than the mark of a marker on your skin. The marker mark is probably only a micron thick while the soap residue will completely envelope your hands so ask your self do you want all the residue in your tank from washing with soap, or just rinse with fresh water and leave behind probably close to nothing.