1 Use a wine yeast --it will ferment for longer as beer and bakers yeasts are killed off by lower concentrations of ethanol.
2 Mix your yeast with a teaspoon of warm water and some yeast nutrient from the home brew shop (a little vegemite will do also)
3 Put the mix in a small bottle with cotton wool in the top and keep it warm until it is working well (producing bubbles)
4 Add to main sugar mix and connect to system.
Yeast multiplies in the presence of oxygen and ferments in the absence of.