I used 2 cups water, 2 cups sugar, 1/4 teaspoon yeast, 1/4 cup of 100 degree water for rehydrating/activating the yeast first. tmix i got from a site that was writen by John LeVasseur and all he talks about is DIY CO2 systems. Its called "A Treatise on DIY CO2 Systems for Freshwater-Planted Aquaria. GOOD LUCK! Hope this helps.
This is roughly what I used, except that I boiled it and added a 6oz jello to it. Then poured that into the 2L bottle and put it in the fridge over night. I used 1/2 tsp champagne yeast (very strong, will live to 18% alcohol) and activated it first.
My first mix lasted 3 weeks and then started to decline (but ran for another week). I added a second one to it in week 3. My second one is still going after a full month now. I have since re-mixed the first one that was running out. So essentially I'm running 2 and just swap one out each month once the jello is almost out.
The jello slows down the yeast and the the champagne type will live lots longer. Thus I have to swap it far less often.