What can I mix and store Kimchi in?
To mix, use any bowl that won't be damaged by the salt.  I would stay away from metal or wood, anything else would be fine. 

To store,  just use a glass jar. I usually use a half gallon canning jar, but if you're making a lot you can use a gallon jar.

Cover the cabbage with a big flat cabbage leaf.  (Or a grape leaf).  Press down, so the leaf is covered with brine. Next you just need a weight. What I like to use for this is a plastic bag: get a big one(like the kind you put produce in at the grocery store), and fill with some water.  Put that in your jar on top of the cabbage leaf, being careful not to spill any water.