I use cheesecloth to filter out my kefir from the grains.
I then rinse the grains with filtered water.
Kefir grains are not real grains. They are a symbiotic colony of bacteria strains that form little gummy semi-translucent "grains".
There are milk kefir grains and then there are other kinds that can be used with coconut milk or water. I use milk kefir grains.
I use pasteurized half-half from the grocery store. I could use raw milk, but this is a bit cheaper. I only drink a small amount at a time or use it to ferment other foods. I use some in my daily smoothie.
Kefir needs to breath, so I use a sprouting lid and keep it in the fridge to let it ferment slowly. It is good to use within a day and will continue to get more sour. It also good to stir vigorously on occasion for helpful aerobic fermentation.
You should use it within a week or so if you don't like it too sour, but it is still healthy and safe to drink when it does get sour. It just might be too sour for your taste buds.
You can get started by getting your own grains on Amazon.
The Organic Fool