If doing it as prep for service work...You can pump the brake pedal.
incidentally, your coach may have 1 or more automatic drains. Our Freiightliner has one. I am under the impression the Spartan Chassis may have more than one.
The auto drain, will open for a short time each time the governor reaches compressor unload. You probably don't hear it...only because the Air Dryer also purges...and makes more noise.
Unless something changed... Newmar cables are all the same appearance. So you have to know what goes to what. The Spartans have color coded cables. There is an order to which cable gets pulled...because there is a cascading order to how the tanks fill. If you get the order wrong...and water is actually in the tanks...you'll transfer water. The "wet tank" is the first one...and it feeds the Secondary and Primary tanks. So, you want it dry first. Then the others. If you look up there and examine the tanks...you'll probably only see two. It's deceptive. There are walls built in to some of these tanks... which make it more than a single tank. My Freightliner (Ventana) has the WET, and SECONDAY in the Driver's side wheel well. The PRIMARY tank cable is by itself in the Passenger side wheel well. The Suspension system also has "PING" tank chambers it uses that are hidden inside the overall tank design. You may be able to see the welded seams on the tanks where these dividers are located.
If you have a Spartan...ask any owner...they will most likely know the code for the color sequence. I just looked at my tanks...and followed the cables out thru the frame rail. I added a Label to the rail by each...so I don't have to try to remember what they are.