My apologies if this comes across rude, but I don't believe you have read the whole thread or you may have seen the million times this was brought up before. You can use a balloon with a pinhole in the top or you can do what I did with mine.
http://imgur.com/idxdn.jpg
http://imgur.com/GQfWd.jpg
Using an oxygen tube and some black electrical tape I do the same thing but can direct my CO2 usage more efficiently. To test it I just stick the tube in a glass of water and give the bottle a shake and it lets me know if the CO2 is still being emitted.
YOU CAN USE A BALLOON WITH A PINHOLE IN IT IN PLACE OF THE DOUBLE LOCK VALVE.