I faced this same issue on the Ford, and now that I have Pacific Dualies wheel liners on my Chevy, it's a similar situation.
Here's what I've done:
First, the kit:
compressor, double foot straight gauge, valve extender, 11/32nds hose

I've installed these short extensions on both motorhomes now, neither has been an issue over the years. I tightened them to the original valve stem with tiny adjustable slip-joint pliers when I installed them, and to date, never had a leak:

For the inner dual: peering through that "handhole" that some Ford "engineer" should have had their head examined....:

Simply use the 11/32nds hose to reach in and remove the cap:

Result:

Reach in with your double-foot gauge to check the pressure:

If you do need to add air, use one of those dastardly extensions attached to the inner dual shrader. The female end of the hose is fixed - it will not rotate independent of the hose. Thus, it can be installed by twisting the hose:

Attach your compressor:

It helps to have a screw on fitting, where the push-on style is difficult when holding the push-on to the hose, and turning on the compressor. two people (or three hands....) would be helpful. One of the push-on type with the hold clip would help, or having a large compressor that has a holding tank.
This setup would work on the sprinter as well.