Clogged Waste Tank

[prestadude]

I just got back a few hours ago driving our coach from Newell to Sacramento. This was the last step of a very long process that started in May, 2009:
1. Mid-May 2009 - Purchase coach, shuttle from Phoenix to Sacramento
2. Early July 2009 - Drive coach to Indiana for handicapped conversion work
3. Mid July, 2010 - Handicapped conversion work done, drive coach to Miami, OK for Newell to fix some things
4. Mid October, 2010 - Drive coach from Miami, OK to Sacramento

So you can see, even though I have owned the coach for 1.5 years, I have only had possession of it for about 1.5 months. I added this preface so you can understand why I did not understand how the waste water system works.

Right after I arrived at Newell on Wednesday and was hooking up water to the coach, a helpful owner at Newell came over and pointed out that the manual valve to the waste tank was shut and explained that the valve allowed discharge of grey water only. I had only dumped the tank once (or so I thought) on my drive back to Indiana. It turns out I only dumped grey water that had backed up in the plumbing (I remember looking at the tank level readout after dumping and thinking that the sensors were misreading and were probably dirty). I only used the toilet a few times on the way back to Indiana so this problem was there when I picked up the coach in May, 2009.

Well, last night in Bakersfield I finally got the manual valve open using considerable effort and a pry bar (visions of the scene from the movie RV flooded my mind). Unfortunately, opening the valve did not result in a flood of > one-year-old doodie. I only got a trickle. I added water for additional head (increase from about 1/3 full to 3/4 full), still no effect.

Well, my plan of attack is as follows although I would be interested in suggestions from the group.
1. Chemical - I read on the Internet the report of one fellow who used a chemical called Rid-X to unclog a tank. I will use that chemical (or something better) to convert the mass from a solid to a goopy liquid (I am getting the dry heaves just writing this).
2. Pneumatic - Convert the driver side discharge from "dump on the road" to something more useful by adding a cam and groove fitting with a plug. Install a gland fitting on the plug so I can insert a rigid plastic tube into the tank with out leakage. Open the driver side valve to the waste tank, push in the plastic tube which will be connected to a compressed air source (maybe 30 psi) and try to fracture and liquify the mass with bubbles. Kind of like a poop jacuzzi.
3, Mechanical - using the same gland fitting, advance a metal rod with the tip bent 90 degrees. Hook the rod to an electric drill and spin to agitate the mass (I guess I don't want to get it too agitated, remember Steve McQueen in The Blob).

Suggestions? I will go out shopping for the chemical tomorrow.