I received my grains and my grains are growing!  basic questions, please as I am new to this.   When can I start adding more milk to make more kefir?  Does it matter? (started with a pint) Can I use the same container and not wash it out and simply add more milk?  (It's what I've been doing.)  Should I clean it periodically?   Where do people find the containers they use to strain easily?  I hea…