You don't need a tranny "flush kit", but if you want to keep things simple, get a tranny filter from IPD. Around $25. Then you can just cut the tranny hose, flush the system, and install the filter. You will need to save a couple or three milk cartons to collect the old stuff, and a clear PVC tube from a hardware store (5-6 ft)and 1in clamp to fix it on to your tranny line.
The 850's/X70's need about 12 quarts to clean nicely.
I, too, am waiting for slightly warmer garage temperatures to do my cars.

Klaus
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98 V70Rawd(101Kmi), 95 854T(85K mi), 75 164E(173K mi)