I’ve found the disks from http://hawsepipe.net to be the most useful study tool around. Taking a few practice tests tells you very quickly the areas where you need more study. Once your routinely getting an 80% or 85% passing score on the practice exams, you shouldn’t have any problem with the USCG exams. The disks also come with a bunch of Navy training manuals for reference. Mid Atlantic Maritime Academy has a one on one test prep for about $1k / week. I don’t know of any courses specifically for 3 A/E though.