I own a Cookshack. Cookshack says there is no need to pre-heat. I never have and never will. SmokinTex says there is no need to pre-heat their smokers either. BUT if you do, make sure the rack or racks are out so the meat will not stick. Cold meat on cold racks. Also, wear heavy gloves when pulling the woodbox to load with wood. Whether it is SI or CS or ST, all say not to use the smoker without the woodbox in place.
As for cleaning, I wash my racks after use. As for the interior, after removing the foil from the box lid and the floor, I wipe the floor with paper towels to remove any dripping that got under the foil. If any of the seasoning is peeling at the ceiling, walls or door, I wipe or brush the loose stuff off. This is all done the day after.