I didn't take the Testmaster's FE prep, but did take their PE review course. What I can say about their courses is, they use instructors who are familiar with the exams and the content of the exams. They concentrate on teaching material to "get points." It is not their goal to teach you the material, but rather to teach you what you need to know to get enough of the easy points.
Passing these tests is as much about what you know as it is about using good exam strategies. You know you won't get all the questions right, and you should not waste time on questions that you know you can't get. An educated guess is sometimes the best option on difficult questions (the testers have to write the tests to be challenging enough to stump even the brightest test takers once in awhile).
I would highly recommend some kind of test prep course -- Testmaster's has a great record of success with serious test-takers.
Your comment "just keep on studying on my own and hopefully pass" concerns me. You need to develop a positive attitude about your ability to pass this test or you beat yourself before the game begins. Believe in yourself....you graduated with an engineering degree, so you have the skills and knowledge to pass this exam! A review course will give you exam strategies, and focus your studying on the most likely question topics and types. There is so much content in an engineering curriculum that you can't know everything and it can be overwhelming.
GOOD LUCK and bring on that positive attitude!!!!!
