Tonight I was soldering some feeder wires. I didn't have anything handy to hold a 22 gauge feeder at a funny angle against the track. I grabbed the first thing handy--not often a good idea--which happened to be a razor blade held by a typical safety handle. I used the sharp side of a brand new blade, which it turns out "grabs" the metal wire you want to solder very tight due to the sharp blade edge. No slippage. You can apply as much pressure as you need to and you can hold the blade anywhere, including right in the middle of the solder because the mechanical connection to the sharp blade edge is so small it falls right out of the solder without even the slightest grab.
Now, there's probably something, somewhere wrong with this method. Is it enough to worry about? It worked extremely well.