Several DIY Yeast CO2 System questions.

For any who may be familiar with the 2-liter-soda-bottle method of CO2
production... using baking soda as a buffering/stabilizing
compound... Could someone tell me what the optimum mix of water,
yeast, and baking soda would be using this method? (in case it makes
a difference in the formula, the yeast culture in this case is an
ethanol-resistant strain commonly used in wine-making). Also, how
often would one recommend refreshing the solution in the bottled
culture? Or would it be best to discard the culture and start a new
one? If discarding, how far in advance should the new culture be
started to supply a consistent amount of CO2?