Ok So I have one air tank already... Question though.. (I have 1 5gal tank, thinking about buying another)

How can I run a 125psi setup from both tanks and have my gauge read both tanks pressure and also take air from both tanks (ie when I pull the cord to my air horns or pump up my tires)... Would I run them in parallel and attach fittings accordingly? I just want to be able to keep my pressure over 100 most of the time without having to turn on my compressor...

So with that said, can I use my compressor to fill both tanks at the same time and not go over 150psi WP on the compressor? Just curious...