The previous owner is correct, the taste and odor of pink RV antifreeze is hard to get rid of.
Completely drain the tank using the outside drain. If the tank runs parallel to the long axis of the trailer, raise or lower the nose to get as much out as you can.
Since you have already winterized the rest of the TT, you're pretty much all set. I do the same thing. I disconnect the water line from the tank to the pump when I winterize because I never got around to installing the winterizing kit. Since I have already drained the tank, I raise the pump end of that hose up a bit so it drains.
What little water is left in the tank and hoses can not break anything when it freezes. The drain line on mine is a soft plastic and won't break. In both hoses, any residual water won't matter because it is a small amount and is not confined. When it freezes, it can expand lengthwise in the hose and not break it.
I leave the drain open all winter. When I de-winterize, I fill the tank part way to do the clorox sanitize routine. I don't close the drain valve until I am sure that it has flushed any bugs, etc. out of the drain line.
'12 F250 4x4 Super Duty PowerStroke 6.7 diesel
2011 to present: '11 Cougar 326MKS
1999 to 2011: '99 Sunline T-2453
Amateur Radio kd2iat monitoring 146.52