The BSA Guide to Safe Scouting, Chapter VII talks about how BSA runs its shooting sports program. Basically, if someone wants to become a Rifle and/or Shotgun Merit Badge Counselor they must do the following:
1. Become an adult leader with a BSA Troop or Venture Crew by filling out an adult application and completing BSA Youth Protection Training (online)
2. Submit a BSA Merit Badge Application (specify Rifle and/or Shotgun Merit Badge Counselor) and attach a copy of your NRA credentials showing you are an NRA Certified Instructor for the discipline you want to teach
3. Once accepted, follow all guidelines in the Guide to Safe Scouting when running the shooting activity
Innovative Defensive Solutions offers the NRA Instructor courses and the NRA First Steps Pistol for the Boy Scouts of America.