Get a quality pressure gauge. Most important. I haven't had any luck
with the two digitals I bought, but I really like the dial ones.
I would be ashamed to let someone look in the drawer where I keep air
fittings, tire valves, and gauges.
"Why do you have so many?" someone might say. <G>
Well, we have a GMC 2500HD, an S-10 Blazer, a Lincoln MKZ, a Hyundai Accent,
a Holiday Rambler TT, a 2 ton capacity utility trailer, 2 wheel barrows, a
hand truck and 2 bicycles.
And you're right; the dial gauges are the best. I have 2 from Accu-gauge.
The rest are only good for "approximate". <G>