Will do it good to be started rather than left standing even longer IMHO.

take the oil feed to the turbo off, and pour oil down it, to backfill it to the pump, and pull the king lead off the dizzy so you can turn it over.

2 years isnt actually that big a deal though really.

Leave it running the whole time he is washing it, and try and make it a monthly ritual to just go and idle it for 5 mins, stops one set of valves being open the whole time and corroding and loosing seal.