I use store bought lumber, typically pine or cedar or plywood. Typically I assemble the project (e.g. toy box) and then the surfaces with an orbital sander and/or hand sanding in the inside corners. progressively using finer grits until I have the finish I want. Have considered purchasing a drum sander to pre-sand all the boards and/or pieces before assembly and just need to do final sanding after assembly. 2 questions: 1- Do people use drum sanders on already dimensioned/finished lumber such as purchased in a retail lumber yard? 2- Lumber purchased in such stored typically are not completely flat. Can a drum sander be used to flatten the bioards?