yes the coke bottle idea is the best i put mine in tank as its warm and they hatch faster
the brine shrimp you have looked at on trade me are decap not hatching ones but stu ( the same guy) also sells hatching eggs
THESE http://www.trademe.co.nz/Home-living/Pe ... 471805.htm they should last through a discus batch.
i find that my bbs only last 3-4 days as it gets used all up so on day 3 i start another batch and they should be ready but the next night (because of being in the tank = warmer)