Deleting all the data is definitely the slow way and no there is no one step tool for that. Far faster to dump a .df and build a new database, though.
Back before temp-tables we would keep around an empty database which a sort of generic table in it for building reports. By copying that DB, attaching it, using it, detaching it, and then just deleting the copy we eliminated 2/3 of the overhead in actually trying to clean up a copy for reuse.