My solution of current pickup on brass locomotives.
They pick up one pole on one side of the locomotive and the other in the tender.
And it's via spring blocks .... It doesn't work well on digital.
I replaced the gearbox cover with a piece of circuit board laminate.
There is not enough space on the underside, so I had to sand the laminate 1 mm.
The holes next to the gear are filled with epoxy for strength.
The pickups are phosphor bronze which has a small spring coil made by wrapping the wire around a 0.7 mm drill bit.
The power cables are soldered to the old pickup points.
Now you have full power pickup on the locomotive, now the tender trucks will receive the same treatment.