I agree with the last 2 posts, its important to have fresh solder on the end of the tip. All rosin core solder has flux in it, you can get liquid flux as well but I would use a combination of both, the liquid flux will let it wet better, if you need to touch up a joint use the liquid flux then tin the tip and put the tip on the joint. I'm not sure about the wattage but I have soldered lead solder Sn63/ PB37 which is standard electrical solder up to 850° no basic iron will ever get to that temp. I have soldered deans connectors and mine is a cheap iron, just have to hold it longer on the solder joint and has never damaged the connector. Also when you are done soldering tin the entire tip and unplug or turn off, you won't have to replace it for a very long time. Also do not use a file on a tip unless its pure copper, some of the higher end tips have tin impregnated in the metal of the tip, you will shred it with a file.