I don't use too much hands-on as have been mckenzie trained but when it's required i use it. and can certainly get a bad thumb if i don't do it right. I have 2 techniques: put the thumbs back to back straight arms and apply pressure with body weight - and the thumbs support each other. This may not work when the PIP joint drops backwards I guess so the second posture I use is to hold one thumb with the other hand and support it like a splint - again using correct bed height and body position to apply pressure.
As I said earlier I often get away with using exercise therapies and patient generated forces with the same if not better results. I do agree there are times when hands on is required and in those times I try to utilise a good technique but otherwise I do quite well to avoid it.