Average water usage?

My truck camper has a 42 gallon fresh tank and 30 gallon gray. We typically shower outside when boondocking to reduce gray water tank fill. Because I have an enclosed trailer in tow with toys, it is outfitted with two more 42 gallon fresh water tanks and 30 gallon gray tote that makes our camper capacities comparable to a toy hauler (which we previously owned). The gray tank contents fit perfectly into the tote and the additional water tanks refill the camper or are used directly through a transfer pump run off batteries in the trailer. We have found places where it is not legal to dump gray tanks in the environment yet outside showers and vehicle wash downs have not been restricted - Using the additional tote capacity even allows us to shower inside if the weather turns bad.

I had considered using compressed air to drive water out of my tanks, but I typically only carry a low volume high pressure compressor which would be running longer than my transfer pump to access water.