I found the Marine 16 bug stuff works well, I would be surprised if the fuel treatment stuff didn't. I intend to get some and use it when I next fill the tanks.
Not sure if this helps but.. When I last cleaned the tank out I then 'rinsed' it with a gallon of paraffin. And having an inspection hatch, a scrubbe on a bendy stick ( coat hanger) will wipe the base stuff loose..
A wet vac is ideal of course
And... According to many and various Premier Marinas notices, they add treatment to what you buy from them.. But you are a ways from one of theirs at the mo..