I'd recommend some "Mind Games" too.
Mind Games (version 1.0) by M. Shirley Chong
TONS of submissive pee links here -
Can We Help You Keep Your Pet? Submissive Urination
And I'll try to work on the vid for you
Often time, a VERY enticing treat like tiny bits of cooked hot dog, will distract a dog so that peeing is the last thing on his mind (not that the peeing is something he can control).
And so as soon as you get the dog up, you shove your hand with the bits of hot dog in it, into his mouth, and YUM, good dog! As long as he's not peeing.
Thing is - he's learned this and it's embedded behavior so it's going to be tough. Also it's difficult as humans to deal with the piddle so we get disgusted no matter how we try not to be. Even knowing it's not his fault is not helpful at times, I GET THIS.
Your goal is to ignore EVERY SINGLE incident of submissiveness. If you're working with him and he starts squatting or rolling over, WALK AWAY. Do not pay one bit of attention to this. Only show affection/attention when he's NOT submitting/rolling/squatting.
How I know this, is we had a dog like yours, a very submissive GSD who you just know people smacked because he'd piddle submissively. I knew that because he'd go from cowering, squirt of pee to "Oh my GOD I'm in for it now!!!"
And we'd ignore it, clean it up with no ado and he gradually got better but we still had to trim his nails on linoleum because he'd piddle every time.
We also had a Dachshund, came to us at age 6, same way, very sad stuff. These dogs were smacked usually, as puppies, for the training mishap, when it's nothing of the sort.
Anyway - PM me any time to "vent" if you need, I completely understand your issues!