I would buy 188 deg solder and 145 deg solder from the UK. Eileens emporium is the best adress for that with a great service (an low postage). I use 9% phoshoric acid as flux. Electical multicore solder is not good for kitbuilding.
TEE1055, my three daughters used to help me too till they discovered boyfriends. Then it was not so cool to help dad "run" trains . Please remember what I advised about the bogies. Lastly I will be placing more detail photos in this topic over the next few days.