Yes thanks Richard.. Not sure how you mean about blowing dust into the lens..  The rear elements are sealed.. But much the same as with the Camera a good technique is to hold the lens and camera face down to the floor with the openings downwards.. As long as you take care to not protrude the blower too close to the sensor or glass, the effects of gravity will then encourage any dust to fall out..

Danny O'Byrne  http://www.digitalartzone.co.uk/

"All the technique in the world doesn't compensate for the inability to notice" Eliott Erwitt