I use a Flexzilla 1/4" x 25' flexible air line from Amazon with my own air inflator/deflator that I assembled from readily available brass fittings from Ace Hardware, air hose fittings from Harbor Freight (or Home Depot), a 3' flexible leader hose I found on Amazon, and a 0-60 psi gauge from McMaster-Carr (P/N 4089K62):
In inflation mode:
In deflation mode set up to deflate two tires at once:
The inflator/deflator alone:
One inflates by attaching the green air hose to the coupler shown to the left of the inline valve (with red handle). The inline valve with red handle is kept open unless one wants to isolate the tire gauge in order to get a reading without any fluttering of the gauge needle. One deflates a single tire by connecting the red hose to a tire and opening/closing the thumbscrew drain valve shown to the right of the gauge. One can deflate two tires at once by closing the inline valve, attaching the red hose to tire #1 and the green hose from the coupler to tire #2, re-opening the inline valve so the two tires equalize pressure, then deflating both tires at once by using the thumbscrew drain valve.
Everything (including other inflation accessories, spare parts, fuses, etc.) fits in this bag that sits behind the driver's seat:
Why did I go to all the trouble when a simple air chuck and separate gauge would do? It all started when I decided that I was tired of bending over to inflate/deflate tires - the 3' leader hose on my inflator allows me to clip on the chuck and stand upright while I inflate/deflate/check tire pressure.
Sure its overkill, but why build something when one can overbuild it?
The compressor:
Caveat: This airline and all fittings are set up for an open chuck system that one typically finds with a portable air compressor or a hardmounted compressor that doesn't utilize a tank. If one uses a tank then one would use a female coupler at the end of the leader hose rather than a stud, reverse the green hose, the quick connect coupler next to the inline valve would be replaced with a quick connect stud, etc.