Best way I've found to solder on those bullet plugs is find a way to hold your plug upright (pliers with a rubber band around the handles or something). Then take a mini torch and heat up the plug. Then start filling the hole up with solder until it's about 3/4 full. Then quickly stick the tinned wire all the way into the hole while the solder is still real hot and liquid. Hold it there for a few seconds and shrink tube it and that's it. Much easier that way than with a soldering iron.