75 mins is fine. As others have said it is peak time, DXB is fully open 24/7, and no one has to clear immigration or customs for transit, unlike US airports.

After he arrives he will see blue and red signs, blue for arrivals to DXB and red for connections. DXB is incredibly well signposted (after all about 9 million pax use the airport every month!). Follow the red signs (and the crowd of People from his flight that'll mostly be going the same way) and he'll arrive at transit security. Remove anything that'll beep in the metal detectors (sometimes shoes beep, sometimes not), go through, collect everything and then look at the bank of screens to find his connecting gate (he might be able to see it before landing on the Airshow channel on the in flight system but good to reconfirm in case of a gate change).

Have him look at a terminal map of DXB before departure so he's got the layout roughly in his head, for EK concourses A, B and C will be relevant, all 3 are used exclusively and in their entirety by EK. He may arrive at a bus gate, the bus will drop him off at transit security at either B or A, while getting off the plane he should look for a person holding a sign with destinations as usually there are two buses, one for A and one for B. The one for A has a list of destinations, if his connection is from A, then DPS will be listed, or else if he saw in the IFE that his gate is an A gate ask which bus is concourse A, else just go to the other bus.

Overall, follow the signs, get to the connecting gate first and foremost, once he's got the actual gate in sight and if he has another 15 mins he can maybe pop into a nearby duty free but I'd not recommend it. It can take 20 mins at a brisk pace to get from transit security to the next gate if it's far, if the next flight is boarding via bus they tend to board it quite early.