How much air does it take to unlock trailer brakes?

Thanks for the replies guys. Been on the road a while and haven't had time to mess with it. I am going to try the glad hand with a valve and quick coupler and hook an air hose to the trailer and see how long it holds. That is a slick idea I never thought of. I have a compressor on my pickup so I can air it up wherever the trailer sits.

 

And thanks for the pics. That is a slick set up for a wheel loader. I think I will need something shorter for my skid steer though. I have picked up the front of my 53' step with it and it does it fine but I don't know if it would that far out.