Soldering larger QFP type devices: You can use the solderpaste and
the above method for soldering these too. However, here is a
soldering iron method I learned from a guy who re-worked PCBs on a
production line.
Prepare the pads with flux. Place the part down, hold it and use the
iron to tack down the corner pins. This is important...if you get the
1st tack wrong you can heat it up and remove the component...if you
get more than one area partially soldered you will need a hot air heat
gun to remove it!!!
Once the part is positioned and tacked, go over the pins with the flux
pen.

Gel flux from a syringe is much better as it minimises the chance of
bending the leads. I find that the solder flows better. as well.

Leon