[reno911]

As a recommendation never file you tips. Most are plated and that plating is what for the most part carries the currant to conduct the heat. After soldering leave some of the excess solder on the tip don't clean it. This will prevent oxidation and prolong the length of the tips use. If you need to file the tip weller makes a cleaning bar that is less abrasive.

My recommendation for hard to solder, 8 gauge type, pain in the butt things is to tin the tip of your solder pen/gun with a lucrative amount of solder. Rest the wire onto this little pool and wait till the wire reaches temp, which is a bit quicker this route than without the extra solder, then feed the solder onto the wire end. After you have done this place the wire to the connecter and heat the wire to the connecter, which again may take a bit so if you need tin the tip of your pen/gun a bit to speed up the heating procedure.

All of this i do on a regular basis with a weller 60 watt solder pen/station. If your leads are presoldered than the more the better