You can do a Liver Flush basically whenever, not "only" after a parasite cleanse. (However, if you strongly suspect or know you have parasites, go ahead and cleanse them first as sometimes they can make you feel a little ill after a liver flush.) Just pick a protocol/recipe and flush away! Many people, myself included, just love Clarke's quick and easy Epsom Salts , olive oil, and grapefruit juice flush. Cheap and painless.
There must be literally hundreds of parasite cleanses available, many can be bought at your local health store or organic grocer's. Black-Walnut hulls, cloves, and Wormwood are the main ingredients to look for, other anti-parasitic herbs include gentian root, hyssop, black seed, pumpkin seed, thyme, peppermint, fennel, grapefruit seed, the list goes on. ParaGone has been used successfully by many people here. Look around and see what's available in your area.