It is best that you use the recon drone to clear out as many enemies in the area as possible before you start marking the target. To mark the targets, you must look at that area you need to mark first, hold down 'X', then from there you can turn an shoot anyone around your recon drone. If you drone takes too much damage, it will be destroyed. A new drone will be provided, but it will start back at the beginning and you will have to fly it towards you.
Make sure you keep moving forward when you have an area cleared out. It seems that there is an unlimited supply of enemies until you make a push.
Make good use of your flashbangs. I would recommend having at least 2 left after you place the beacon on the bridge. You will want to flash the guys that are on the double set of stairs that lead up to where the helicopter dropped in some men. The last flash you have should be used when you are on the ships deck near the first beacon. You will want to throw it into the group that is running towards you. This should give you enough of a distraction to run past them.
You can earn the dr0n3d achievement as well on Veteran difficulty, but it is very frustrating. Once I completed this the first time, I ran a time of 3:50. I will have a video up here shortly as well.
On a side note, If the recon drone is destroyed you dont get a new one you fail the mission and have to start over if you are playing co-op for this mission. Thank you to OneManMafia86 for this info.