How to reflow a part in an infared IR rework station?
My procedure when I've occasionally done this in the past with QFNs &amp; TQFPs is:
 - gently but thoroughly clean the pads. 
 - apply fresh paste
 - place the new part with the help of a vacuum pickup and microscope (and sometimes start over because I smudged the paste everywhere)
 - then carefully move the board back over to the IR station for reflow.
I'd usually apply IR from below and hot air from above at the same time, and generally end up successful.