Air supply on road, pretrip for short runs?

My air compressor is not in really great spot to get close to. Without blocking yard. I have one tire it gets low after 2 weeks sitting. I filled it to 50psi 110v compressor Saturday AM. Monday still over 40 psi.
Where do you plumb in? I could of course go in tanks. BUT the trailer has a pintle hitch, air spot. *I have not looked but I assume still hooked up?*
So IF so what about trailer side glad hand? Should be able to find one. Then +20’ air hose? From rear that should reach back 8. From tractor should reach all 10.
When truck, to trailer unhooked. *unpressurized* brakes of course set. But if I used from back of trailer which would I use to keep truck, and/or trailer brakes set. So using red ones would brakes be on if I took from trailer rear red ones?
It’s a 04 Volvo with a grain hopper trailer.
Darn. Now see complete unit, 50’ hose $40 delivered. Why play with short stuff.

 

I thought I could be cheap. Use short hose, rear connector. But $40 premade? Ordering it. I was thinking $15 end, $10 other, $50 for hose, then adapters. But compete

 

I see no reason to get excited about it. I am hauling my own grain about 35 miles, then back empty. It sits for hours, days, weeks… I need a new tire gauge as mine does not fit well. It could be less then 5 psi a day.
I have a car that needs air one tire monthly. Take it in, they can’t find anything. Spray soapy water. Then dunk tank with pressure to hold it under. Then flip, try again. “No leak” but in a month I feel it, week later car TPMS light comes on. Right, rear tire 5 psi low.
Please tell me how I am a danger? One dual gets low pressure, I fill it. Right now likely only mid 70psi as no gauge, awkward to fill as well. I just can hear it thumping a bit. Decent gauges on order, plus airline;glad hands