This is a problem that continues even when you have a job. Depending on how busy your service is, you're going to maintain certain skills just by doing them a lot. But there's always going to be things you will need to revisit periodically to stay competent.
I'm personally facing this right now as well, as I haven't been on an ambulance in 3 years, and am looking at going back into the field next year.
Part of the answer is probably recertifying the alphabet courses, which for you as an EMT, is probably ITLS-basic and CPR. For me, I'm looking at PALS, ACLS, and probably NRP (if I can find my way onto a course), as well. But these aren't even a minimum, they're just things you have to have to get hired.
If you know other people in the field, especially people in clinical education this can be advantageous. If you find someone who's had a lot of students, they may be able to give you some scenario practice. Definitely re-read your textbooks, and class notes.
Maybe you can find somewhere where they'll let you ride along as an observer. This may be a quick route to a job in a smaller service, even if they're not actively hiring. If you make a good impression on a ride-along, they may be interested in having you as a casual staff member.
There's also lots of good resources on-line, just keep to your level of training and scope of practice, unless you're sure you're solid with that. It can be very tempting to start looking at higher level skills, which is fun but not necessarily productive.