Make the Rib Juice for basting a day ahead. Simply whisk together the ingredients and store in the refrigerator in a plastic squirt bottle. Take out to warm up to room temp before using. The Rib Juice will help keep the meat moist and tender and is also great for "dry ribs".
Plan on cooking 2 1/2 hours. Load the firebox mixing in smoking wood if you like smoke flavor. Start the cooker 45 min. ahead of when you plan on cooking so it is fully heated and stable at 350 degrees with an indirect setup and a raised grid. Plate setter legs up, drip pan on plate setter and grid on legs is a standard indirect setup. I like hickory or apple wood when smoking spare ribs.
Trim off excess fat from spare ribs, remove the membrane from the bone side and using a spoon, scrape off fat deposits along bone. Lightly slather yellow mustard then dust with seasoning rub to both sides.
Place the two spare ribs flat, bone side down and side by side in the cooker. Check dome temp as there might be a drop in temp from the cold ribs. Slight adjustment to the vent may be necessary to slowly get back up to 350 degrees. Cook for one hour.
Flip spare ribs to bone side up, baste bone side with Rib Juice and cook for another hour.
Remove ribs and change setup to direct heat raised grid. It is important to be at or near gasket level with the grid when grilling direct so the spare ribs do not burn. Set spare ribs back in the cooker bone side down and baste Rib Juice on meat side. Grill for 10 minutes. The cooker will jump up in temp, keep under 400 degrees.
Flip ribs bone side up and continue basting with Rib Juice or you can brush on BBQ sauce at this time. Grill for 10 minutes.
Flip ribs bone side down, baste with Rib Juice or brush on BBQ sauce to meat side and grill for 10 more minutes. Then your done!
Allow the ribs to cool for a few minutes before serving while your family and friends go crazy with anticipation. Enjoy!