I think the big key to the process is using Fido jars. I have a couple Bormioli Rocco blue lidded jars that I just love - they have a great solid seal, and the blue glass lid is so pretty. The thing about Fido jars is that they let excess pressure leak out, but they let no oxygen in - no oxygen means no molding.
I like not having to worry about things like that. The other thing that ensures it, of course, is making sure your containers, utensils and work surface are all clean and sanitary. So, with that out of the way, here's all it takes:
1 head green cabbage
1 head red cabbage
4 T. salt
Large sharp knife
Large mixing bowl
Large serving spoon
Fido jar (50oz or larger)
Wash and dry your cabbage, removing any worn outer leaves. Cut the cabbage into chunks, removing the cores. Feed the chunks through your food processor set to grate coarsely. As processor gets full, turn the grated cabbage into the large mixing bowl, and sprinkle with some of the salt. Continue to process and salt the cabbage until done.
Cover the bowl loosely and let it sit about 1/2 hour - the salt will start releasing liquid from the cabbage. Using a potato masher, pound the cabbage for a couple minutes to more completely release the liquid.
Scoop cabbage into Fido jar, mashing it down as you go to fit more cabbage. Make sure all liquid from the bowl ends up in the jar - the cabbage should be covered with liquid.
Seal the jar and set it aside in a dark place with a moderate temperature (70-80F) for 4-6 weeks, then refrigerate.