Arrachera is also known as Hanger, Skirt or Flank steak depending on who/where is selling it.I have had tremendous success smoking fajitas on the WSM and the Lang 48. I buy my meat (arrachera) at a Mexican market close by. What I do differently is I do not have the meat sliced in half and tenderized. I smoke the whole pieces of beef. Once they reach 135°, I pull them, slice against the grain and throw them in the crock pot with the vegetables for about an hour. If you have a Mexican market nearby, talk to the butcher. Ask for the thickest pieces of beef. Remember: do not slice in half, do not run the meat thru the tenderizer, cook it whole. You will not be disappointed.
This would be the similar to my last recommendation except smoking first and then braising in the Crock-Pot.
But to me the meat really needs a charring/searing somewhere in the process for optimal flavor in fajitas, carne asada and such.