"I would bring with you 3-4 QTS of ATF for use in a flush on top of what your AT requires. Then request they purge all the fluid from the new fluid container. They may need pushing on this.
Then the flush with synthetic can begin.
One thing to keep in mind, these guys are not going to value your ATF like it costs $9/QT, so they will use some to purge their machine, you need to decide how much is reasonable".
So I may fully understand this. I need 2-3 to prime the machine, in addition I need additional ATF to "purge all the fluid from the new fluid container"... Please expound on this part, matter of fact the whole statement???