It would be very useful if BRU could process all files in a folder and it's subfolders in a single step. It is boring and time wasting to jump from folder to folder to apply the same pattern to files.
I think it already does that. If you go to Selections (12) pane at the bottom of BRU and put a check mark beside the Subfolders option, it opens up all the subdirectories to expose all the files.