I'm not sure what the adjustable wrenches method is, but I've used a different method which while typing, enhanced. Maybe I read it somewhere, maybe my brain does work?
So, my previous method is using a threaded hub axle. It fits the threads of the hanger. Thread it through and you have the ability to adjust on infinite plains using it as a lever. This has worked for me just by eye, but my enhancement is to add a flat washer or plate and bolt against each side of the hanger. The flat plates will give you an indicator of where the hanger is bent. You can then align using the axle as a lever, in very small increments, adjusting the bolts and plate as you go until straight. Or perhaps even tighten the bolts up, so that the plates align the hanger?
The hanger doesn't look too far out, and you'll not need to put a lot of force through it to align. Keep the wheel in place to keep the frame aligned and you should be golden.