I am still very new at this, however I have done a total of 4 racks of spare ribs now, ( two smokes ) and can at least share with how I did mine.
I put the rub on my ribs, the night before - cleaned them, removed membrane, rubbed them and sealed them up in plastic wrap, and put in the fridge.
The next morning, got my smoker as close to the 240 mark as I could. Since I was doing spares, I used the 3-2-1 method.
Layed out the spares on the cooking grate, meat side up. Sprayed them good with a 50-50 mix of apple cider vinegar and apple juice.
Kept an eye on the temps throughout, and opened the lid every hour for the first three hours and sprayed them good again with the above mixture.
The 2 hours after the first three, I put them in foil, sprayed real good once again, and sealed the foil up and returned to cooking grate. Actually for one of my smokes, the weather was horrible and had a hard time maintaining temps, so the 2 hour sealed in foil for that one, I actually did in the oven at 240. The other smoke I kept on the smoker the whole time.
Unwrapped them for the final hour, gave one more good spraying of apple cider/juice mixture. Last 30 minutes, I basted with barbeque sauce.
I can say both smokes, the ribs did not have a piece of dry meat on them anywhere, they were really good.
Others way more knowledgeable than me can help you more, just thought I would share my experience - and I did these smokes from the knowledge I gained from this forum.