Just caught up on this -
Fat Rat. Bloody good on Your
Is there any rust in the tank, or just 'gunge'? Only way I have ever cleaned out tanks (many years ago, on a 2-stroke single, and a Bonneville) was ball bearings (or new, small, nuts and bolts) and petrol and lots of tedious shaking of tank, empty, rinse, repeat. I probably sniffed more vapours than was good for me, though
Afterwards I assiduously kept the tank full of fuel as much as possible - filling up after a run, for example.
There's probably a magic spray that does the job, now
PS: great advising there, Pat
Hope you aren't still snowed in over there!