Trans flush with no convertor plug...

This fluid is done, I cant see how this black stuff (an inch over the full mark too) could be good and of course I drained it into a dirty pan with a few leaves and treed droppings into it so its not reuseable. Its a FWD Mazda with the Ford/Mazda 5F27EL transmission. I took the valve body out and back flushed all 6 of the servos , they all spec out in OHMs and all click with power. Cleaned the valve body and i didnt find any metal particles in the pan so I think its just a high mileage auto with the normal fuzz on the magnet. On a few recommendations Im using 2 gallons of Walmart high mileage ATF instead of $16/qt Type M ATF that I guarantee no quicky lube place has on hand. Heck, its special order at my Oreilly and Vatozone. Itll be an experiment for sure. Does a 727/904 even pump through the VB in P? I thought at a minimum you had to put it in N...?