Hi all. Found this info while spending too much time researching recipes instead of cooking! Hope it is of some interest. Have included the whole recipe for the info on squeezing. I'm of the just ok butter makers, and need to improve my technique.
Homemade Butter
We found that ripening the cream a bit first—in essence, culturing it—yields a more fully flavored butter.
Start by pouring a quart of the best-quality organic heavy cream into a large bowl; then cover the bowl with plastic wrap and let the cream sit at room temperature (ideally, around 68 to 70 degrees Fahrenheit), undisturbed, for six hours so that it begins to sour slightly. In the meantime, line a colander with cheesecloth and set it inside another bowl.
1. Begin slowly whisking the cream using a balloon whisk; as the cream reaches the soft-peak stage, speed up the whisking motion.
2. Butterfat, in the form of tiny granules, will begin to accumulate on the sides of the bowl as it separates from the buttermilk (the liquid portion of cream); continue whisking until the butterfat granules are about half the size of a pea.
3. Pour the entire contents of the bowl into the cheesecloth-lined strainer and let the mixture drain for several minutes.
4. Gather the ends of the cheesecloth together and squeeze, pushing downward to extract as much additional liquid as possible; then unwrap the butter solids from the cheesecloth. (Reserve the butter milk to use in your favorite biscuit recipe, if you like.)
5. Pour cool water over the butter and rinse, carefully squeezing and folding the mass in on itself, until the water runs clear.
6. Put the butter into a bowl and sprinkle it with 1⁄2 teaspoon kosher salt.
7. Using a wooden spoon, smear the butter mass repeatedly against the side of the bowl to aerate it and thoroughly incorporate the salt; pour off any additional liquid the butter may release.
8. Using the wooden spoon, transfer the salted butter onto the center of a piece of wax paper and form it into a single, smooth-sided brick.
9. Wrap the butter tightly in the wax paper and refrigerate it overnight before you use it, to allow its flavor to develop. It will keep for about three weeks.
From the American cooking magazine, Saveur.
http://www.saveur.com/article/Recipes/Homemade-Butter