What do you use for dually air pressure gauge and inflator

Good chuck will have ribs inside to hold on the valve when slightly tilted.
This way you can lock the valve and leave it for the time it will take to inflate big tire.
For inflation, read the label on the door to start with.
When front tire pressure is easy to figure out, the rear on dually will change a lot with the load.
When my dually empty should have like 30 psi, the fully loaded comes to 80 psi.
When you drive empty with 80 psi, you better have good dental insurance.