....... "Currently I'm working on the tender with details and need to add electrical pickup to the wheels for the decoder.".........
I am in Nscale, that said, what I do for electrical pick-up in tenders (w/o elec-pickup), box sound cars and cabooses is to use heat stripped wire wrap wire, and wind a coil, about 6 turns, around the axels. This only works on wheel sets with only one wheel isolated, the other wheel is electrically connected to a metal axel. There is maker that makes wheel wipers, I forget the name.
PS I have one truck pick up one side and the other truck pick up the other rail. I se ONE wire to wrap BOTH axels on a truck leaving a long end to feed up into the car.
BTW NICE job