I am happy that you all are finding and using this knowledge...for the parasite formula, I would use Vodka to tincture or make the extract.
The garlic oil you crush the cloves, and cover them with organic olive oil, cover, and set this in a warm place for two weeks. You could use your oven (keep it turned off) for example, or as you correctly stated, always keep your tinctures jars covered or in dark bottles.... or cover with dark paper, etc. Light degenerates and breaks down the extract, making it useless or weak, so you are right, keep it covered, or in dark bottles, or in the dark.
It's very important to SHAKE SHAKE SHAKE your tinctures or extracts every day!!!!!!!! ;)