How to focus on list of found files after search in Finder using the keyboard with full keyboard access activated?
An ideal solution would be a single key press that is relatively intuitive and consistent with other keyboard interface rules. Nonetheless, I have found a couple of hacks that seems to work. 


Cmd+[ then Cmd+]: This navigates back then forward. After this has occurred the focus is on the file list. A mild nuisance with this option is that the search is refreshed, which can lead to a brief lag.
Cmd+Shift+G followed by escape: This opens the go to folder dialog box; escape exits the dialog box and returns focus on the file list.