THe key to soldering is put the heat where you want the solder. I will usually tin the inside of a connecter, and then the wire. Then heat the conector until you can pusth the wire in and hold the heat for a few seconds to see the solder flow. It helps to have a fresh tin on the solder tip also as that allows a better flow ofthe heat to the piece.

I've not experience with the Deans conectors, but i seem to remember a good article on making some pin holders to use while soldering. Maybe someone else can point the way to that article.

Don