Can I offer a suggestion here...

A pull pull conection when soldered will have no place for the hot air to go except out the end that you are trying to solder...forcing the solder back out...
If a small hole is drilled towards the threaded end for the hot air to escape and that end heated the solder will be pulled towards the end with the hole in it and filling up the conector and the wire at the same time...
Ya will still have the same strenght out of the fitting...

Stay Brite solder is finikie...too hot and it won't flow...too cold it won't flow...