Newbie question here - what does "flex drill mean?" I'm a brand new DCO, it was suggested I join a particular unit at my NOSC, I looked up the unit and it shows they "flex drill" with three day drills three months per year. That's 18 drill periods, so what happens to the other 30 drill periods?
Specific to the Navy Reserve, some units only meet a few times a year for 'mandatory' drills while the rest of the drills you reschedule and perform for various reserve related tasks from training and medical to supporting your unit and everything in between. The unit CO should lay out their expectations of what they expect you to do those drills you don't utilize on the mandatory drill weekends.
Most unit CO's I've dealt with had the pretty reasonable approach to flex drills, allowing folks one or two to take care of their annual medical and dental requirements and a few to deal with GMT and personal administration stuff (ID Cards, preparing for promotion boards, etc). As long as you were just generally reasonable and didn't schedule 8 drills to do your medical, 11 drills to do your GMT or 20 drills to 'do admin' most CO's were pretty flexible with 'flex drills'. That said, I've known guys in units where it has been a much more rigid and inflexible approach, but those were usually not 'flex drill' units which are inherently more...flexible overall. That is usually, I had a buddy in a flex drill unit that was anything but flexible for several things, helped him to decide to retire a little earlier than he planned rather than put up with the BS.
Other than those 'administrative' drills most units I've dealt with usually want you to use the flex drills to support the unit or the supporting command your unit is attached to in some fashion, in what fashion is usually up to the CO or may be delegated to your department head. My last unit supported numerous exercises and many folks would reschedule drills to support an exercise, utilizing IDTT if available. Sometimes we would also have training related to the unit, not GMT, and folks would often utilize their flex drills for that as well.
Finally as you get more senior you will find yourself utilizing those flex drills to perform your unit job like CO, XO, admin officer or even resked officer (big enough units with max flex drill often needs someone to herd the cats with rescheduling). In several of my reserve jobs I would often do 1 to 3 drills a month just to handle unit administrivia.
So ask the unit CO what the expectations are for the unit and the flex drills, there is usually no issue in emailing them directly to ask about a unit, and once you get in a unit ask the other folks what they do.
With so little formal training on the ways of the Navy Reserve asking reservists what their own experiences are is usually the best way to learn so if you've got more questions ask away as we have several experiences reservists here.