Hi Rob, I had the same problem printing with an inkjet printer. If you look very carefully, one side of the transparency paper is shinier than the other side. You have to make sure it prints on the duller side. It will still have issues with being clear. The black areas on the gobo will have little lines where the ink printed. The gobo itself doesn't look bad, but when you blow it up on a wall it is VERY evident. Using a laser printed give you more flat color without the lines. Great Video!
For those of you having the same trouble as I, that is: getting the dark areas dark enough, I came up with a solution. First, my Brother inkjet MFC-J825dw won't get it dark enough, period. The quick dry, $1.40 a sheet transparencies suck at that price, so I take it to Kinkos. Now, Kinkos couldn't get it dark enough either, so I had them place what they printed on a copy machine, turn the dark ALL the way up, and it worked! They did it for $.99 a sheet so it's just the trouble of picking it up.
I wish you did these about 2 months ago - I finally cracked printing mine last Thursday! As MrBklein says, on some papers there are 2 different sides - it took a lot of experimenting between my laser and inkjet to get the best results ... and they still weren't really as good as I wanted - I'll post my solution after your next video ;o)