Hey Dude...I don't believe that co2 will be of much use to you. Molasses is used during the flowering stage. Two tablespoons per gallon every 2 weeks.
The thing with co2 is it seems to be an ongoing debate, my feelings from exp and research is that you need a high light environment. It does work though if you have the correct environment, my babies grew about 1.5 inches in 8 hours today, using co2.
If you want a low cost method, and care to try it, here is a recipe for a home made brew:
Items Required:
* 10lb. white sugar
* 5 gallon clean bucket W/lid
* 4 1/2 gallons of water
* A piece of toast browned and hard
* A table spoon of dry active yeast (for baking bread)
First boil the water, (this will ensure clean water) remove from the heat and add the sugar. Stir until sugar dissolves. Let cool until water is room temperature (if you don't let it cool down it won't work).
After the sugar water has cooled, float the piece of toast on top of the water. Now, empty the tablespoon of yeast over the toast. After a few days, the yeast will take over the toast and start making bubbles (CO2) in the bucket. After a week, the amount of bubbling (CO2) will increase.
Keep the lid airtight on the bucket. CO2 travels up the dispersion tubing, and due to it being heavier than air, falls directly onto your plants. Timing your exhaust, is essential in maintaining an effective level of CO2.
Mind you, I've never tried a home made method of adding co2, but I am sure that this will produce co2.
I wish you luck in your grow!
Peace