are you talking the water pan in the smoker, or a pan with the ribs in it? I prefer to cook them directly on the grate for the "3" then foil for the "2" with a bit of moisture, then back on the grate naked the last hour or so to tighten the bark back up a bit. I use Apple juice for pork and beef broth and coffee for beef. I like to reserve the drippings from the beef and make a dipping sauce or gravy with it.
If cooking beef and pork ribs at the same time, expect the pork to be ready sooner as the beef ribs are likely a good bit thicker and will need more time