What I have done in the past is to tin the pads where the parts are going
to be mounted and then I use two soldering irons. One on each pad and it
pulls the part right down into a good position.

Ok ok I hear the question now. What about parts with more than two leads?

That is a valid and good question. Only tin two pads for that part and use
the soldering iron on each one of the pads to get the part mounted and in
position to finish soldering the rest of the leads one at a time.