There is such a thing as a "Solder Sleeve". They come in 10-12 gauge and 16-14 gauge. (actually 5 sizes to 0.275") They are a shrink tube with three round inserts. Center insert is solder, with a low initial melting point. Color circles at the ends identify and when the tube shrink, they also shrink to assist in holding.
Basically thread one wire completely through the tube, strip both wires and intermingle the wires. Then pull back into the tubing centered under the solder. Then heat, concentrating on the solder. I use a simple heat gun, middle setting and like a round reflector to get both sides at once. Concentrate your heat on the solder until it melts. Tubing is clear so easy to see. When you feel you have a good weld, shrink the tubing on both ends.
Usual able to get a good weld first time, but might take a small learning curve.
Easier, although more expensive then doing it your self. Although with practice, an understanding of how to strand the wires for hot solder and shrink tubing you can do the job.
These things are wonderful for coaxial tubing in getting a good ground wire. Unwrap and fold back the wire mesh ground. Slide a striped wire under the mesh and put into the sleeve. Now you will have the two (or three) wires for connection coming out one end. The other end you will have your coaxial cable and the new wire you are using for a ground. Heat the solder welding the wire mesh to your new ground wire and then shrink the tubing. You will have coaxiel and ground coming out one end, the connector (red/ yellow/ black) coming out the other.
Anyplace you want a soldered/shrink tubing connection these will do it. Trailers, trailer lights, boat electrical, etc. Like I say, if you have soldering down pat, stick with it. If your soldering skills are iffy, try these.
I get mine from Crow Bar Electrical supply in California.
Woody