It took me four months to get a job and twelve to get on an actual ambulance. I don't think my "skills" really degraded that much. Lets be real here, anything we learn as a basic is just not that complicated. Most of its common sense, and the more tricky things like traction splints or what have you are tricky because there are different types. Since you won't know what type you'll be working with, there's not much to practice.
What really dies are assessment skills, and it's not really because you forget them. Yea you might screw up the order at first, but until you get out assessing real patients you aren't able to develop any sort of flow to them, and you aren't going to be thinking about what your finding and that's what really counts. I think scenarios are helpful to a degree in that they get you thinking about what signs and symptoms are indicative of what illness, but most scenarios are trying to lead you to one answer (at least in the textbooks). As we all know, real patients are often more complicated than that, and many patients have more than one significant issue that may or may not need to be addressed.
I found this site helpful in making me think about my own practice before I got on a truck, but only to an extent. I was also in a local FD's good graces from a high school job shadow program and they let me ride a couple shifts over the summer before I started, but honestly I did it more because it was a good time and I was bitten hard by the "EMS bug" and really wanted to run some 911 calls. But even if you can find a crew that's cool with this, you can't hope to get enough shifts to get confident without becoming a burden.
So with that, I say put your effort into getting a job and volunteer if there are departments around. Also, relax. You'll remember more than you think. Once you get hired it might be worth going back and reviewing the nuts and bolts like age specific vital signs ranges, your medications, and anything you think has disappeared from your memory.