I've done 2. On one, I used a monster aluminum pipe wrench, rented from the tool store, on the companion flange itself, on the outer diameter. On the other, I used a piece of 1/4"x2" steel bar with drilled holes and ground out pinion nut socket relief, long enough with a pipe cheater to reach the frame rail as a stop. Both were a pita, as the nut is at forty zillion foot lbs.

Locking nut is single use, but I locktited the old one back on.

Not responsible for advice not taken...