There you have it. Any ole compressed air will do (it's free). And, it too is a science.
And, 118 psi in the fronts with 107 psi in all the rears works great,.... if you have what I have. The original tires are still on it, and have never had a problem. I carry a homeade air compressor arrangement that has a 3-1/2 hp Briggs/Stratton (I can lift it with one hand). And, I use a high-quality digital gauge (check them all the time, at ambient temp).
I'm in the process of replacing the tires, just in case there's something to the belief that RV tires should be replaced according to age. Also, if I could decide which one suits my needs, I would buy a pressure/temp monitor.