James, I am the Lead Training Officer for my FD and we had the same issue that you are having now with the same few members showing up for trainings. We solved this problem by eliminating the training night/department meeting, etc...and replaced it with on duty shift training.
I developed a weekly training schedule and every shift officer is responsible for conducting the training for his/her shift. Naturally, the shifts that have one of the Training Officers will be more involved but at least every member working is training and we are all training on the same topics at the same time.
The Training Officers are also assigned a few topics throughout the year and they are to make a presentation for the entire FD. This keeps the Training Officers sharp, gets the shift officers involved, saves money by doing most of the training on shift, and it gets the training out to the members. With patience, accountability, diligence, and prayer this has worked great for us.