Assuming you've already removed the drain plug from the water heater and drained it. Then left the plug out. And you've removed any water filters you have.
Try to park in a way that puts the drain tubes (lowest point in the water system) further downhill than any water might be. Then make or buy something that will give your air supply a way to tightly connect to the shower hose inside the house. That's the highest point in your system.
If you have a washer, those faucets are fairly high, so do those first. The washer hoses should have air blown into them with the washer on 'Fill'. Then switch it to 'Spin' to empty the pump.
Start blowing air and have someone walk around and open the faucets one by one. Starting at the faucet furthest and highest away. Slowly work down to the outside shower.
After all the faucets are open, keep blowing air, have the helper turn the various faucets off/on several times to 'jog' left over water.
Eventually you'll only get air out of the faucets. Or some sputtering.
Newer RVs have PEX plumbing that is 'resistant' to freezing. Having spent 3 winters in Fairbanks, Alaska, I can attest to that, and to the air method working fine. The tiny amount of water left over in your pipes shouldn't be a problem.
I've never done the air method on a very unlevel surface, but if I did, I'd drive the RV afterwards with the drains open, and try to park opposite of how it was parked before and then blow it out again.
Some might think it's just easier to go ahead and use the pink stuff on an unlevel surface.
