Have a truck with air brakes? Drive it over and use the engine driven compressor and a hose to fill up the tires.

Otherwise removing wheels or a portable tank sounds easiest/cheapest.

Or something like this... in one form or another has been around for about 100 years http://www.aerostich.com/engineair-power-pump.html

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-