I have two smokers, one a wood burning smoker with an offset firebox and the other is a pellet smoker both purchased from Yoder in Hutchinson, KS. Both units came with small drip buckets but depending upon what you are smoking there will be grease well distributed on the interior. In the pellet smoker, I have a second shelf and what I do is put an aluminum foil baking pan and put it on the first shelf while the food goes on the second shelf above. In addition, the heat diffuser which evenly distributes the heat across the surface of the pellet smoker is covered in foil. Just replace this foil and you are good to go again
This is not possible in the wood smoker since I only have a single grill. Below that grill is a heat management plate that distributes the heat across the grill from the firebox so that 2/3rds of the grill maintains the same temperature. The other 1/3 rd of the grill closer to the firebox gets progressively hotter closer to the firebox. Fat just drips to this plate and to the surface of the interior below. This really is not that difficult to clean and the whole unit can be cleaned with paper towels in under an hour. Any grease that I catch in the drip cans is transferred to a coffee can that we keep for grease disposal.