I am in the process of learning how to grade coins properly and am quickly learning the benifits of it which include. 1. Not getting taken by sellers who are trying to pass on inferior coins at a higher grade. 2. Being able to cherry pick better coins from sellers who may not have graded properly- resulting in great savings. 3. Being able to feel confident in the auctions that I list so I don't cheat myself or others. As I said, I am still in the process of learning and am finding out that the small details matter greatly.
Have you looked into the ANA's summer seminar? they do amazing grading classes, i've taken three of the week long classes in as many years and have learned an so much!
An less expensive, but a help for mint state coins is the ANA produced DVD on this page. I have it somewhere as a VHS tape, and watched it several times a long time ago. 2nd one down. Jim http://www.brent-krueger.com/video.html