From: http://forum.studebakerdriversclub.com/showthread.php?92216-Soldering-Tips%28!%29



////Removing old solder and reapplying new.../////



 Having solder residue already sticking to it will make it easier to solder new wires to it. 



You might try compressed air when the solder is melted. Be careful where you blow it. You probably can't get the wires uncoated completely but down to just a surface coating. 



a quick shot of compressed air can blow away excess if it is not given a chance to cool. A quick swipe with a dry cotton cloth can also reduce the residue.
Just like "sweating" pipes, a minimal clean adherence of cold solder to the wire will facilitate a good joint. In plumbing it's called "tinning." The end result is you are joining solder to solder, rather than copper to solder to copper, if that makes sense. 




If the existing/leftover solder is bright and shiny, with no voids or black spots, it's as clean as it's going to get and ready to accept fresh solder.  A trimmed to size piece of cheap sponge, wetted with water (not dripping, just wet) will wipe "hot" solder from where it's sitting.
Note, a wet sponge will also keep your soldering gun/iron tip clean. Just wipe the hot tip across the wet sponge, retin the tip, use as required.




never, never ever dip your tip in the flux. (For some reason, folks new to soldering always want to try that!)





for electrical solder you must have rosin cored solder. Never use acid flux solder on any electrical repair. The acid corrodes the wire, and it also sets up a .07 resistance, while not much, it is a point that will heat under current flow. 





You need either a 63/37 or 60/40 rosin core lead/tin solder for electrical work. Do not use solid core solder or acid core solder as they are not acceptable for electrical work. If you can find a Radio Shack that is still in business, they will have what you need or a place like Fry's Electronics and many hardware stores will also have the correct solder. Bud