Trying the Lionel method:
With all the wires needed in the boiler for the LED lights, there is limited room for more weight so I've put some nail polish on the back set of drivers on the B&O EM-1 2-8-8-4 and it seems to work quite well on increasing pulling power.
Since the initial test of just nail polish on the back engine set, I also did the same with the back drivers for the front engine set. I'm only doing 'double' on the articulateds. The 'straight' one set of driver engines will only get nail polish on the back drivers.
I used a q-tip and some alcohol to, first, clean off the tire.
The engine is run about 5 MPH and the nail polish is applied while the drivers turn.
The brake shoes also had to be removed on this model as they were too close to the drivers and the paint would have rubbed onto the brake shoes.
One loses 'pick up' power on this driver but this procedure doesn't seem to affect total conductivity.
Will have to see how long the nail polish lasts but initial findings look promising.
I read about 'frog snot' but some reviews said it wasn't as effective as promised.