I have no familiarity with the Spray Nine product you speak of although I imagine it couldn't hurt with all the various concoctions many use to keep their black/grey tanks happy. We purchased a simple, low-end tank wand nearly 10 years ago at Camping World when on a shopping spree to equip our then new TT.
Just 3 little holes on the head, but it sure does shoot powerful streams that easily restores our tank sensors capabilities such as they were from the factory. We installed an internal tank flush/rinser that does a decent job most times, but is no match for our $6 tank wand in removing residual build-up. We use tank wand every 4 or 5 trips out.
