Here is the spray port located on the side of the camper:
It looks very much like standard "air hose/compressor" fittings but, it is not interchangable. They are slightly different. However, they do operate the same.
Here is the spray hose with a standard garden hose "pistol grip" sprayer. Any garden hose sprayer will thread on. Also pictured is the "Y" with individual shut offs (the pressure reducer is the brass thing).
As you can see, the camper can be connected to one "leg" of the "Y". Another hose can be connected to the other leg of the "Y". With the above, I already have a pistol sprayer to put on the end of the second hose. However, if you want to splurge, buy a second nozzel for the end of the second hose.
I should add that I have never tried using the sprayer, plugged into the spray port, while hooked up to city water. I assume it would work. However, I think it would not flow as well opposed to the above arrangement. Plus, it saves a little wear and tear on the spray port seal.
The "Y" is nice to have. I once was in the situation where my water supply hookup was broke and there were no ther campsites available. The neibors were kind enough to let me tap on to their's. Also, I figure if the valve on my city water connection on the trailer decides to blow out/malfuction, I can screw this thing into the side of the camper, shut the valves to get by until home and I can repair.