I'm sure cow legs are the same as deer, and I've done a lot of deer. I'd keep them out of direct sunlight, and away from direct heat when they start to turn hard, which is a matter of about 12-24 hours depending on size, air flow, etc.
When they are fresh cut they are white, wet, flimsy, and feel slimy to the touch. Clean them well like Dana just said, then lay them out on a cookie sheet or tablecloth (something they won't stick to, NOT newspaper or iluminum foil) seperate them with a small space between each one so that air can get through. Lay them out in the form that you want them in when they are dry (if you want them straight, lay straight, if you want them coiled for easier storage, lay them coiled). Then just put them up somewhere dry, and away from flies, dogs, children, etc. As they dry and harden they will shrink and get crooked somewhat. If you want to hurry the process a little, you can expose them to warm airflow, ONLY UNTIL they start to turn from white to tan colored and the surface feels dry and begins to harden. Exposing thrm to warm or hot air at this point will make them sweat their natural oils and lose strength. It's easiest to just lay them up, go to sleep and forget about them until the next day. When wet they may have a very slight odor, but as they dry will completely lose it and when hard will not smell at all.
Let me know if I didn't explain something or if you have more questions.
~~Papa Matt