So far I've just tested the FR300. Works great for simple PCB, but not really efficient for multilayered boards like computer's motherboards unfortunately.
With all of those layers, pretty much anything you try by itself will struggle (iron, desoldering iron, or hot air). Preheat the board first (say 125 - 150C), and see if that doesn't improve your results and make life easier.
As per what to use, a used or cheap hot air preheater plate would be ideal (I've a 110V version of an
ATTEN AT853A that ran me ~$62 shipped using a discount code <Tenma label on mine>)*. But if you can suspend the board somehow (I use a Panavise), you may be able to rig some way to direct the output of your hot air station to the underside of the board. Another potential solution would be put it in the oven (parts on both sides prevents using an electric skillet).
* Added link.I was disappointed to see a broken piece of plastic on the FR300 just after unpacking it. It's a very little and useless one, close to the heat gun, but on something at this price it's not really pleasant !
I'd feel the same way.
Contact Batterfly and/or Hakko and see about getting a replacement part sent to you instead of sending the existing unit back for replacement.
Again, thank you all for your advices and especially to nanofrog
You're welcome. Glad it helped.