I was, at one time, an NRA Certified Instructor for Pistol, Personal Protection and Home Firearms Safety. I was also a Tennessee Dept. of Safety Certified Instructor and taught the State required course for the Tennessee Handgun Carry Permit. None of these programs required much more than good basic shooting skill and most of the instruction was geared toward beginners or the average shooter who visits a typical static shooting range once or twice a month.
If your fundamentals need work and you want to sharpen your basic skills then these programs are OK but if you want a fairly advanced course focused on the latest methods I suggest paid training from a reputable facility/instructor teaching the most modern techniques. I have taken training from instructors like Ken Hackathorn (pistol and carbine), Rob Haught (shotgun), (Super) Dave Harrington and others of lesser fame. They were ALL better than any NRA class I've had or taught. Don't get me wrong, the NRA courses are great courses...just not advanced.
Joining a local club that shoots IDPA or USPSA style matches is a lot of fun and can be an excellent source of training if you approach it in that way. Most clubs have reasonably proficient shooters who can also instruct...not all can do it but some can.
I no longer maintain my certifications but I am a Certified IDPA Safety Officer and Safety Officer Instructor. I also teach an intermediate and advanced Defensive Pistol (advanced pistolcraft/not advanced gunfighting) course to friends, family, club members and other select individuals (for no fee) just to keep my instructing skills sharp. There is no real certification for most of the advanced pistol training that is available but many instructors keep their NRA certifications current for insurance and business reasons. The NRA courses, at least the ones I'm aware of, are not really intended for advanced training.
IDPA Member A00640
Founding Charter Member - Middle Tennessee Shooter's Club