For vintage bikes I just use a large cresent wrench and my eyeball to get things aligned. For 9 spd and above, that tool would probably be nice to have but having to adjust a hanger on such a bike is a rare event for me so I don't need to have the tool in my basement. My co-op has one as does any decent LBS.

Checking the hanger is a must on any aluminum frame,as even with replaceable hangers they can be hard to source and/or expensive. On steel frames, as long as there are no cracks there shouldn't be a problem although a really bashed up hanger often indicates a poorly treated bike.