To clean and lubricate the freehub body on a current Mavic freehub you need 5mm and 10mm hex keys:
– remove the axel-end cap on the non-drive side by pulling it out
– insert the 10mm hex key in the nondrive side and the 5mm key in the drive side. Unscrew in a counterclockwise direction and remove the axel.
– lay the wheel on its side, cog side up
– carefully, while watching for the flying pawl springs, rotate the freehub body counterclockwise and pull up, removing the freehub body
– clean bits, then reassemble putting 10-20 drops of lightweight oil into the freehun.
hope that helps – extract from Zinn and the art of mountainbike maintenance which I can highly recommend!!