DEC selection follows the same format as for FO.
As you will not have the benefit of 4+ years in the right seat to assimmilate the Emirates way of doing things, the assessment of your CRM skills will be more intense, and your management of the non-normal events in the simulator will also be graded to a higher level. Other than that, you carry out the same tests. Obviously your interview will be more indepth.
As far as I know, your sim evaluation follows the same format as for the FO, but for some reason it tends to be longer than the FO one. Sorry, I don't know why, just waited longer for the DEC candidate to come out than the other FO guys.
For some reason, in the past the selection failure rate for DEC candidates was quite eye-watering, so come prepared to take a bit of a beating as you will be grilled. The company expects you to be 100% from the day you walk on the property, there is no bedding-in time.
Good luck.