I have only cleaned out the bottom of my UDS one time in the past year. Everything comes out with the ash pan or is burnt up in the charcoal. I add new charcoal and clean off the ash pan before each cook. No grease to clean up in the bottom of my UDS. It stays clean.
Ash pan is a 20" harrow disk.
22.5 WSM, 120 Gallon Offset, Weber Performer, IQ-110, ET-732