I took a couple of Besser courses about 8 or 9 years ago when I was transitioning from power electronics to RF. I did not absorb everything right away because I had zero RF experience but it was a great way to get a jump start. No short course is going to make you an instant expert but they can at least expose you to the issues and specifications.  Material I had learned in school but forgotten, like s-parameters, came back to me after taking the course. I did not immediately grasp some material I had never seen before but when I needed that material on the job, I knew what to study. In summary, the Besser courses were definitely worthwhile for me.

http://www.bessercourse.com/