I have often entertained a theory much akin to what you describe, I have in the past had success with blowing compressed air through stubborn solenoids. Pour ATF on the passages and activate the solenoid a few times, while also feathering a little compressed air through them as well. A couple of well respected trans rebuild shops in my area swear that if you get ATF hot enough it will actually gell. In fact they just package all of their rebuilds with a product that they refer to as "cooler douche". The stuff works very well and I really don't want to know what is in it because I have to think that it is some pretty nasty stuff to cut through the crud that it does.

Being able to stand up and do a solenoid is a huge advantage for sure but a flex-head gear wrench in 12mm is really awesome as well. One of those tools that when you buy it and use it you wonder "where have you been all of my life"

Mark