How do you get a large blob of solder?
Clean, secure, flux, heat, rest.
Clean the rail with a fiberglass scratch brush. They're inexpensive and available on Amazon eBay and other places. You should do this on new from the hobby shop rail, you MUST do this on older oxidized rail.
Secure the wire in place, you can do this just by holding it.
Apply flux. Use an electronics flux. I've never cleaned flux after soldering rail, but it's necessary for PC boards.
Clean the tip of the iron, then apply solder to it.
Touch the iron to the feeder and push it into the webbing of the rail. The flux will sizzle and just enough solder will transfer from the iron to the rail and feeder.
Remove the iron and hold the wire in place without ever moving it for a second or two while the solder cools.
You'll never get a solder blob using this method.
