I'm quite good at straightening bent alloy hangers, with the caveat that everyone, without exception, gets to understand that I'm trying to bend something that shouldn't and that if it snaps or cracks it is simply doing its job and being sacrificial. If it breaks you're paying for a new one.
If you lock a 10mm axle into the hanger it makes an excellent pointer. The mech pivot needs to be in line with the rear axle. Slip an old handlebar over the pointer and bend. Gently but firmly. A bit at a time.
Don't ever try it without the wheel in the frame . . .