Soldering is not rocket science... I started doing it when I was a kid. All I have is a cheap Weller iron from 25 years ago, and I've soldered together a hundred cables, trailer lights, car stereos, etc. and even a few circuit boards.
I'm sure flux is necessary at times, but I've never used it on electrical soldering. I use it soldering plumbing, but that's a completely different deal.
The simple rules:
1) You could potentially dribble hot solder on your work surface, so if you are working on your wife's/mother's nice dining room table, find a scrap of wood to use as a placemat.
2) Heat the wires with the soldering iron and apply solder to the wires, not to the soldering iron. Until the work gets hot the solder won't melt... eventually it will... once it starts to flow, hold the heat there for about 1 more second to allow it to flow evenly, then pull the iron away.
3) Sometimes you need 3 hands. A pair of pliers and elastics works, or maybe a roach clip...