Cleaning is a little hit or miss. The smoking chamber and the firebox are lined on the bottom with heavy duty aluminum foil. I empty the ashes before each smoke. The ashes go into a galvanized trash bin with a tight lid to extinguish any coals. My neighbor set his house on fire with week old ashes from a grill that still had some live coals hidden inside. Every third or fourth time I remove the foil in the smoking chamber and wipe down the chamber with paper towels. I use a spackle knife for stuff that doesn't come off. When done, I wipe down with a thin layer of vegetable oil.
I clean the grates every time before starting with a grill brush and scraper, followed by wiping off with paper towels. I follow this with a coating of vegetable oil.
I'm going to try the salt cleaning next time.
Citrus oil cleaner is a no go. Green or not, it doesn't work very well and leaves an odor. It is not worth the cost. Ditto for any kind of oven cleaner. Soap and water are also no go. My smoker is made of thin steel and I avoid any kind of rusting like the plague.
At the end of the day, the grease buildup is more cosmetic than hygienic. Most of the buildup is in lower temperature areas where it doesn't vaporize anyway. Grease also protects against rust.