Well, I’m not exactly sure if it’s new or not but I’ve never heard of it before. Discovered it yesterday while building an O scale turnout.
I wanted a particular shape for a metal frog, so rather than just dumping solder on a piece of brass, I took #14 copper wire from a Romex cable and bent, shaped, twisted, and layered the wire to form the #12 turnout frog.
Then, I heated up the wire. The entire wire heats up almost simultaneously because copper is a great conductor and one strand of copper is all that you need. Then, once the flux started bubbling, I applied the solder and it took to the exact shape of the copper frame.
A hacksaw blade was used to carve the flange pathway. The dremel cutoff wheel didn’t perform very well in this task as the solder is very hard.
The same technique could conceivably be used to model a piece of metal in any shape you desire, be it a piece of detailing on a diecast locomotive, to a switch stand; let your imagination take hold.