How do you rough in for surface mount disconects that install after drywall?
I would leave sticking out and fixed rigidly sticking straight out a section of MC,  for the sheet rocker to know that it needs to stick through the rock.  Leave a couple of feet in a tight coil to give you something to work with on trim.  On trim I would take a beefy screw driver, stick it into the hole in the wall and pry the straps loose.  Then once you connect to the disconnect you can shove the slack back into the wall.

Second method, more difficult.  Do the work to get your EMT connector just in the right position sticking through the rock to come.  Put a rigid coupling on it for protection and a short nipple of EMT just so the sheet rocker won't miss it.  Leave a coil of wire hanging there for the trim.  On trim pull off the pipe you don't need and slap on the disconnect.