Originally Posted by the incubus

2 things you need to do to remove factory wires quickly…

First, place a bead of flux on the solder joints and then be sure to apply a touch of solder to the tip just before touching the solder joints.
The solder on the tip of the iron means you'd be touching the existing solder at maximum sustained heat and the flux will allow the heat to transfer more rapidly into and through the entire joint.
Shouldn't take more than 2-3 seconds each.

NOTE: You want to use at least a 3mm wide tip. A narrower tip takes longer to transfer heat. If set my iron to 700 or higher and follow those steps I'm done removing factory wires in no time.

When soldering new wire, strip just a tiny sliver of the insulation and tin the ends thoroughly but lightly. Then dip the the tinned leads LIGHTLY into the flux and present into the holes on your
board. You want the wire to sit INSIDE the holes with no stray strands of wire hanging out/over. If you're having a difficult time getting them in the holes fully, you can crimp a tad with pliers until
they seat fully and cleanly. From there, make sure you have flux on the ends of the leads and then touch your tip to it while applying a touch of solder and release.

Should result in a factory-like joint.