No need to chew on the garlic. You migth want to cut it in smaller pieces to swallow it, I did not I would swallow the entire thing. If the smeel bothers you, however, you may choose to use allicin in gelcap instead.
For Grapefruit-Seed-Extract and O. oil, purchase the product and use it according to what is written on the bottle. Divide the dose so it cover the entire day: 2 Grapefruit-Seed-Extract a day, means one in with breakfast and one with dinner.
Some people rotate them every 3 , 4 weeks, some people rotate them every day: a day GSE, a day garlic.