Brass wire is a poor choice for making wipers for the back of a driver or tender wheel. A much better material is Phosphor Bronze. Its slightly stiffer and will not wear as fast as the brass.
Check out Tomar Pickup shoes also. A basic kit comes with enough material to mount up to 4 of their shoes to any loco that needs additional pickups.
But I have had to add these types of pickups to very few brass engines over the years.
My mistake, I've been using the phosphor bronze wire. I've also used the Tomar pickup shoes, but they are a little unsightly. I'm hoping someone has another option.
Really nothing works better that the Tomar track siders and as to them looking ungainly painting them black makes them almost invisible, check my installation where the tops have not yet been painted....you still have to really look to notice them on this brass GN. steamer.
The phosphor bronze wire & tomar pickups are what I would do, though like Carey, I have not had to do this much, only on very short wheelbase locos, like Atlantics.