Get to the airport early and request them is the only way I've heard of for the exit rows. They'll only give you the ones for the upcoming flight so you have to make another request in DXB for the next leg. Bulkheads may be pre selected through Manage a Booking but you may get moved if someone requests a basinette seat.

You can call them with your credit card to hand to change your ticket to Business Class, assuming there is availability.