What is the best method, for a small office, for cleaning batches of maybe 50-100 small PCBs? I'm making small runs of PCBs with a lot of big through hole joints, so they come out basically covered in flux. Cleaning them by hand takes far too much time. Does anyone have experience with a specific method that works well for lots of boards, but isn't terribly expensive? Maybe an ultrasonic cleaner with a specific solution?