Does this method only apply to ribs or can it be used for other meats, Enlighten me!
3-2-1 for Spare Ribs; 2-2-1 is for baby back. Not many other cuts it works with that I have found although I am a foil fan and use it to help get through a stall on longer smokes. 3-2-1 has worked for me on beef ribs as well. Below is a rack of beef ribs I did a while back. They were pretty big and ended up being more like a 3-3-1 to get the result I wanted.
It's really a guideline for ribs ........ even individual racks of ribs cook differently so times vary all over the place. This is a good start point. Sometimes I foil (3-2-1) and sometimes I don't, just cook straight through. If I'm going to foil, I cook my ribs until I get the color and bark I want, then into the foil with stuff they go. I check them at about 45 minutes to see the doneness. Once done, out they come, back onto the grates and follow up with a nice glaze. If cooking straight through, cook until they pass the bend test, glaze until set and eat.