I've had really good luck with using "Michelin type" tire levers, those "s" shaped things with the upturned tip. For lube I use a rich mixture of liquid dish soap and water. If keeping the tire in the drop center is an issue a couple of C- clamps can be used to pinch the together the beads opposite of where you are prying. A tip passed on a long time ago concerns tubed tires, start and end at valve stem area to lessen the chance of pinching the tube. I guess the reinforcement around the base of the stem/tube keeps the tire from dropping fully into the drop center. Over here Harbor Freight sells a bead breaker for about $30 that works great on all the bike rims I've tried along with my wife's Kubota tractor. I've come to almost enjoy spooning on tires as long as enough beer is on hand.