So since we are on this subject, does anyone have advice for wrangling spaghetti QT apps into submission? We have two of them here and of course their creators

So since we are on this subject, does anyone have advice for wrangling spaghetti QT apps into submission? We have two of them here and of course their creators aren't here anymore and we find it very difficult for developers that weren't involved in their development to grok all the shared state.