Yes, you can use the spray paint can upside down. I already tried it and it works. The trick is not to do it too slowly, if you do it too slowly the paint will start falling out of the spray can. I started doing it slowly in the beginning and it was awful. You can probably tell from the photos, I was doing it really slowly and it was really messy. I just kept applying pressure until the paint started flowing out and it worked. I used two cans of paint and it worked well.