You're going to have to get an air chuck designed to air up truck tires. This type of chuck has a foot that faces both toward you and away from you which will let you put air in the outside dual that has the stem facing inward. Can be found at most auto parts stores, truck supply stores, truck stops, etc. This should solve your problem because my MH has duals in the same configuration and that's exactly what I did to solve the problem. The only problem is that you will have to find an air hose with a removable chuck. Good luck.
Dan & Vonieta Stogner
2003 Newmar Mountain Aire, Cummins 400 HP, ISL
2001 Malibu Toad
3 Westies, Charlie, Duffy, and Millie
Think of life as a terminal illness, because if you do, you will live it with joy and passion as it ought to be lived.
If you are on a Ford Chassis with 16 inch wheels the two face chuck won't help much. I have installed 3/4 inch extensions on mine which help some but it's still a hassle. I tried extensions called 135 degree extensions which turn the stem out thru the hole but one of them loosened and deflated a tire. I think they will work if I find appliances to hold them steady.
I had a flat due to a cracked rubber 135deg valve extension ('99 Minnie, 16-inch wheels). Put the spare on and left the valve as is, facing inward with no extension- heck with those! Had no problem checking air pressure with "truck" type dual chuck gauge or topping off the tire with a pump having the same type chuck.