Hmm, placing shield grounds can be "fun" sometimes... I usually like the pot housing, but find a good chassis ground near the pot (pot included) and dont connect it to a ground that is for a cathode, or a volume/tone control, because in my experience, those things can cause noise issues etc. So I'm not sure what the layout of your amp is, but the pot housing should be fine. You shouldn't need any flux, just take some 220 or so grit sandpaper and sand the back of the pot where u intend to solder onto, and it works awesome. Make some clips when your done too! Hope it works out well.