Unless you’re planning to build turnouts, I’d say that resistance soldering is overkill, and, perhaps it is even for turnout building.
To make fast and solid solder connections, the mating surfaces need to be clean: this may involve various cleaning solutions or solvents, along with abrasive methods, such as sandpaper or files.
Once the surfaces are clean, apply a small amount of good quality, resin-based flux. Use it even if you’re using resin core solder.
Your soldering iron should have a clean, well-tinned tip, and should be big enough for the task at hand. Generally, too big is preferable to too small. Allow the iron to reach operating temperature before attempting to make any joints. Where possible, pre-tin the mating parts - this often allows you to temporarily hold the parts together by mechanical means: a quick touch of the hot iron completes the joint.
Where working in areas where excess heat may cause damage to surrounding materials, use heat sinks. These can be any solid metal object - pliers, head of a hammer, or alligator clips. An especially easy-to-use heat sink can be made from wet facial tissue or paper towelling - leave it damp or wet, depending on the job, and as long as it sizzles and steams while you’re working, it will protect the things it’s supposed to protect. Often, the wad of wet tissue holds itself in place, but alligator clips make useful holders, too. When using this type of heat sink, I like to use the largest wattage iron that will fit in the particular work area.
I did all of the soldering work on this locomotive, including building the ladder in-place on the front of the tender and adding details near the plastic turret cover, by using wet tissue heat sinks. Soldering equipment included various irons from 25 to 200 watts, along with a propane plumbers torch.
[IMG]http://i23.photobucket.com/albums/b399/doctorwayne/CNR%20BEEG%20BOY/BeegBo