You can stop cleaning after a job when there is no more paste in the apertures. Under wiping should be done with a quality cloth and should leave no paste on the underside of the stencil (assures good contact on the next print and reduces chances of solderballs) and should leave no cleaning liquid (e.g. alcohol) on the stencil.
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=43352)