How to stop excessive barking?

My German Shepherds are 3 and 4 now. My female isn't the problem, she whines sometimes, makes little yip sounds, but when my male starts to bark he does NOT stop, and it makes her bark too. I've had trainers say "Let them bark it out." Tried that, he will bark for over 8 hours if I let him. Some trainers have said teach him to bark. He barks on command, but won't listen to saying no bark (it's like he can't hear me over himself). Some have said separate them. Tried that too, doesn't work. I have bark collars and that works a little bit. They live in the garage during the day (or the yard weather permitting) and they'll bark at me through the garage after hearing the car pull up without their collars. The collars USED to stop their barking, sorta. Female would bark once, get shocked, then be hesitant about barking again, but still continue if he does. Male will just bark, shock himself, scream about it, and then continue to bark. MOST of the time this happens it is when I am coming home, though they could be doing this when I'm gone and I wouldn't know. I have NO idea what there is left to do. They have a plethora of toys and other things to do, they get lots of exercise (two mile walk or a one mile jog a day). They just do NOT stop barking, at least until I come in the house once I return. I'm sure my neighbors HATE me for it, and I can't afford to keep going to trainers who are yielding no results.

What do I do?