I can understand the concern with a 'power' flush, but I've flushed a few times with my Subaru's doing (what I refer to as) a 'backyard' flush with no ill effects.

You remove one of the transmission cooler hose lines and add some 'extension' hose to route it into a gallon jug (positioned where you can see it from the drivers seat). (If you extend both ends of the line into the jug, you eliminate the 50/50 chance of choosing the 'wrong' line.) (outlet vs. inlet) Drain and refill the 4EAT sump with fresh ATF and then start and idle the vehicle for only long enough to observe 2-3 qts. of ATF pumped into the jug. Replace the amount pumped out and repeat until you've pumped your 8-15 qts (whatever you're comfortable with) of replacement fluid through the transmission.

With a 'backyard' flush, you're not stirring up anything that the 4EAT wouldn't normally be pumping through the cooler/filter.

I've been running Mobil1 ATF (won't run anything but synthetic in my Subaru transmissions) and I shudder to think what a transmission place would charge me to do a 'synthetic' flush. As it is, if I flush a total of about 12 qts., it costs about $60 (@ $5.00/qt.) Still- cheap 'insurance'.......

Works for me.

-Mark