(a) How and when should jars be closed in the cold-pack method?
They are the "open-kettle," the "intermittent," the "cold-water" and the "cold-pack" methods.
For this "cold-pack" method you can use whatever equipment you have in the kitchen.
Blanching is what makes for success in the cold-pack method of canning.
For the salad here shown, tomatoes and beans canned by the cold-pack ...