You'll never catch me putting WD40 in a mill. Not as long as they are selling ARO in shops. WD may disperse water, but it attracts all kinds of other muck too. Da Smak is dead right about long term, WD is not good, it would turn into a gummy mess within a month or so. Osiris, after-run oil and store in a dry (not too cold) place.
Personally, I put 5 fat drops in through the plug hole, give it a quick spin on the starter, 5 more drops in the plug hole, one more quick spin. 5 drops in the carb, open and close the carb a few times. Job done.