I just put 6 racks of BBs (3-top; 3-bottom rack) on the WSM about 45 min. ago. I used a dry rub. They're smoking at 250. Should I spritz them with Apple Cider Vinegar at the 2 hour mark and then every 30 min or so? Any suggestions?

I would wait until the 3 hour mark, then every 1/2 hour. I just use apple juice.

Same here Steve just use apple juice, u can start spritzing as soon as the rub will not wash off, Steve one thing i do is stack my ribs creates a self basting atmosphere, every 45 to 1hr move the bottom rib to the top, try it i think u will like it

Thanks for your advice. I was not able to get out and buy any apple juice - try it next time.
Cooked them about 4.5 hours. They were pretty good. used 4 chunks of hickory. Guests ate em'
up!

I use apple cider for my spritz. Didn't like the vinegar.

I use a combo of apple juice, cider vinegar and BBQ sauce.(portions 2-1-1) Also like to use just straight pineapple/orange juice in a spray bottle.

I use a combo also, mix of apple juice and apple cider vinegar works well

I see no value spraying ribs with anything.
Sorry