Re: Transmission cooler return line
I've done the bucket method, and it took me a couple of hours. Yes, it flushes the converter. However you don't end up changing the filter or cleaning off the magnet.
I've also paid a (budget conscious) shop to drop the pan. In both cases the cost was dominated by using synthetic fluid. I think the shop got a better deal on the fluid than I did, and passed at least some of the savings on. IIRC having them do the labor was like $20 more total in the end. I'll be going that route again next time.
Ideally you'd drop the pan, and then a quick version of the bucket method just to get the last of the fluid out of the converter.
I might have a pan with a drain plug put on next time just to make a more expedient DIY reasonable, but still, that misses changing the filter.
'99 EB ex ENG KSWB news van, low rent 4x4 conversion (mostly fixed by now), home built interior.