Jerry,
After trying just about every conceivable method of cooking spares, I have settled on what must be the simplest technique imaginable. I fire up the WSM (using the Minion Method) and add a few nice chunks of cherry wood. I get the cooker stabilized and smelling good before adding the meat.
I trim the spares as neatly as possible and remove the membrane, then apply a thin coating of cheap yellow mustard (I like Plochman's). I sprinkle on whatever rub I have handy (or simply kosher salt and freshly ground black pepper). I cook the ribs for about 7 hours. I leave them bone side up for the first 6 1/2 hours with no basting, mopping, spritzing, turning, or even peeking. I do not open the lid for 6 1/2 hours. Then I check for doneness (they should be hard to handle at this point without breaking the slab apart or poking holes in the meat), apply sauce (KC Masterpiece in this case) to the bone side, flip, and apply sauce to the meat side. Then back on with the lid for a half an hour. I then pull them off the smoker, let them rest for 5 minutes, cut into individual ribs, and serve. As an aside, I always turn the slab bone side up and use a sharp knife to cut the ribs apart, as it's much easier to get a clean cut without messing up the meaty surface this way.
What I strive for is to keep the atmosphere inside the WSM as constant as possible during the cook, avoiding temperature spikes or drops. I aim for a constant 230-240? at the lid. At this temp, I can cook the ribs to the point of maximum tenderness without overcooking the surface. Keeping the bone side up also helps to keep the meat surface from overcooking. The result is tender meat which pulls very easily from the bone, with just the right amount (to me) of crispy black stuff.
Your mileage may vary, so have fun experimenting! The WSM rocks! /infopop/emoticons/icon_biggrin.gif
Steve