Update: use 3/4" pipe, it's a little heavier but it's a lot easier to control. The half inch works okay if you do not have to go over at an angle, in other words, you can stand directly under where you're using it. But the 3/4" is better. That's what I'm using in the first video in fact. The second video (below) shows the 1/2" pipe version working.
Step 1: Supplies
male and female threaded connectors
plus one threaded angle connector and corresponding parts for each attachment you have in mind to add
red hot blue glue (pvc glue)
cheap broom or window squeegee
possibly also some epoxy putty or friendly plastic
Step 2: Add Connectors to the Pipe Lengths
Step 3: Create the Scraper Attachment
Cut off the business end of the broom and/or squeegee so you have a bit of plastic or metal sticking out that will approximately fit inside your pvc pipe.
The broom was a perfect fit, so I just glued it in with blue glue. I don't know if it will hold, we'll see.
The squeegee didn't quite fit snugly so I'm attaching it with some friendly plastic. If that doesn't hold it well enough, I'll try epoxy putty next.
Let the glue dry for 24 hours before testing it out.
Step 4: Wiggly Woggly It Up There
It works a little better after a recent rain when the moss is wetter and softens up.