Don't worry about bleeding all the air out of the coach, as it won't happen unless you just leave the line open.
To get to 105psi, you will have to catch the compressor on the cycle to increase pressure in the coach tanks (approaching the 120psi cutoff).
You can have someone fan the brake treadle to induce the cycle, but it's much easier to have a method of monitoring the coach air pressure outside at your inflation point, and a method of bleeding air to below the cut-on pressure of the compressor.
It's easy to make a rig using a 1 to 3 manifold (Lowes), a pressure guage, and a bleed valve. You connect your air input to the single connector on the manifold, and the triple output on the manifold has the pressure guage, the bleed valve, and a connector for your short air hose with inflation connector to the tire.
Here's a couple of pictures of the one I made:
When using this rig, the pressure guage shows pressure from the motorhome air system. When you get your tire pressure above or equal to the pressure in your tire the flow into the tire will stop, then remove the air chuck from the tire, open the bleed valve until the pressure guage drops below your compressor cut on pressure, close the bleed valve, and apply the air chuck to the tire again when the coach pressure exceeds the tire pressure.
Fred