I put the prestone flush-n-fill Tee in the heater hose near the sliding
door (this is also near the fuel pump).  I chose that place mainly for
convenience, and because it seemed to serve the same purpose as putting it
up front in the same heater hose.  I flushed cold water into there with the
engine running and can tell you that I had water gushing out the radiator
bleeder, and the rear heater bleeder, the thermostat bleeder and the 1
crankcase drain I could get open, and the fill cap on the expansion
tank.  I just kept flushing after I drained and disposed of properly the
bulk of the coolant.  I would run the engine, not run the engine, close the
crankcase drain and fill and drain the engine multiple times, etc.
Edward