In house education for new and seasoned employees

Hi all, 

I am the education coordinator at Ever'man Natural Food Coop here in Pensacola, the only coop between New Orleans and Tallahassee. I wanted to get some suggestions for how other coops continually educate their employees on the coop world, from product knowledge, labelling, new developments, to basic customer service techniques. I am relatively new at this position (5 months) and I have never had the responsibility of training so many people (I think the most I ever had in one session were 12, and here I have to train and retrain our entire staff of over 50). However, I am up to the task, and I simply want to know how others keep their staff's up to date.

Let me explain my current situation. Our board asked that we implement some product knowledge training. Fortunately, NCGA has a training manual that covers most of these issues. I have downloaded the NCGA training guide and am currently converting it into powerpoints. I have started training our employees in sessions that take place several times a week, and they are all expected to attend one of those sessions each week. I do three throughout the week so that  regardless of when they are/arent working, they should be able to make it to one. This is where my problem begins. I first have to get permission from their department heads to let them take off work. they have given me half an hour each session to train their employees. A half hour to cover what can sometimes be 20 pages in the manual. I then have to go around before each session and make sure they all know about it, then remind the dept heads. Then once the class if over, there is little accountability to see whether they actually learned the information and retained it. 

Basically, I feel as though the training is happening, but it's not as streamlined and as all-encompassing as I would like. I am an enthusiastic guy and I am a good public speaker, but I cant seem to keep up with the process. Too many moving parts, if you know what I mena. It takes me hours to put each class together, and there is not enough time to really cover much in depth, and I wonder whether anyone can really get jazzed about product knowledge when they have been forced to attend. I dont blame the department heads; they didnt ask for this training and I AM taking away their employees in the middle of their shifts. But it needs to be done. 

Anyway, I could use some advice. How do I streamline this process? Is half an hour really enough time? are there any premade resources out there that could help? Any other things that might help this process along that I havent thought of yet? And had anyone ever implemented something like this before and had it work successfully? 

Thanks for the help! Sorry if I rambled on for too long! Thanks guys!