dually tires

Plumbing test ball extension hose. I only loose 2psi when i remove it.

This brings up an interesting point. My dually came from the factory with both valve stems lined up next to each other. The other day I came across something that said the valve stems should be mounted 180* apart. Hadn't heard that one before.

To answer the OP's question; I also use a dual chuck and keep the tires at the recommended pressure - 70 front, 65 rear. Haven't found the need to change the pressures.

I use a dual head chuck, but not that one. I have to use one that is a different angle than that. Pretty much a piece o'cake.

You are talking duallies on the truck aren't you?

Just get a dual head air chuck:

On ours the valve stem for the dual is accessible through the hole in the wheel of the outer wheel. The big "however" is ...I do it because my hands are smaller. If "he" had to try to do so it would be almost impossible. If you have the type of valve stem caps that don't have to be removed that can also be a plus. The next option is to mount valve stem extenders to the outer wheel.

I had metal valve stems installed so both the outside tire and inside tire valve stems are pointed out. Same as filling one tire but do it twice. So much easier than trying to fill the inside tire with one of the dual chucks. Tire-Man Valve Stems

Air compressor with air chuck attached.