After the backdrop was fixed my daughter and I could move on and paint it. The first color we mixed was pretty blue. Too blue. Thus we added some black and white to tone it down. Now we got a nice blue-gray background which imitates a normal day. Now we may add some clouds.
After the paint dried, we created some paper stencils for the clouds. We tried spraying the clouds as I remember seeing in TMTV Juli 2014. I guess we did reuse the same stencil to often. Additionally the spray can was too small and didn’t work very clean. My wife doesn’t like the look of the clouds and thinks they look to uniform. May be we will repaint the backdrop and the clouds later but for now they will stay. Regarding the photos: The camera of my iPhone has collected some dirt, so all the dark fringes in the fuzz in the pictures is not used as backdrop color 😉