This is the advise I got from a grill manufacturer and what they said they use to clean up demo units or units they used in a competition.
As for as clean up I would scrape the interior of the grill down thoroughly, removing any unwanted fuel (grease) from all areas of the interior of the grill.
Then I would run the grill up slowly, 300 deg for 30 min.. 400 deg. for 30 min. (this process slowly desiccates any volatile fuel), then go to 700 deg for an hour or longer if you can. The final high temp sequence will burn off any residual food by- products that are on the interior of the grill.
Then I would shop vac the interior of the grill to remove any ash or dust. Then wipe the interior with a damp towel that you can dispose of when you are done.