If all else fails, my technique is to place a flat bladed screwdriver across the return spring next to the pivot on the side
of the caliper farthest away from the rim, and tap the screwdriver handle with a mallet or hammer using only
the amount of force required to shift the caliper into position.
I have done this for years, and some return springs actually have a notch close to the pivot possibly for this purpose.
However, using a wrench across the flats on the pivot close to the mounting point should do the trick...