Ouch!
Got it off, with a 11mm open end wrench. I left some wd-40 on it for a few days, and then reffed at hard as I could, while holding onto the valve, so it didn't flex the bracket so much.
Took the outgoing line off first, and it dribbled a little bit. The incoming line dribbled quite a bit, and I tried to plug stop the flow for a little while with some rags, and zip lick backs, and a zip tie or two. Didn't work all that well, but I did prevent a big puddle on the ground.
Got the valve body off the truck, but didn't see how much further it could be taken apart. The two cylinders sticking out of it, each have a real flat washer looking nut, that holds them on, but I couldn't get anything to grab those. There was another nut, with a big spring behind it, but that opened a hole that didn't go anywhere.
So just stuck the brake cleaner straw down the brake line holes, and sprayed quite a bit. My hand still feels a little weird from the cold blowback spray. After a few blasts, though, I could get it to spray all the through the valve, but I don't remember which direction it was going through the valve, maybe backwards.
Bolted it back to the frame rail, and then put the front line on. The back of the valve started dribling fluid, and it didn't do that before, so I musta loosened something up.
Its been cold here, so don't know when I'll get back out to the garage to bleed the whole works, and see if it does any better. But I wiped it all down, and then put two clean rags under each fitting so if it leaks, I'll be able to tell later.