I assume that you are going to ETS from active duty and you are looking into AGR opportunities. Its easy to go to Drill Sergeant School as a National Guard AGR or even M-day. The National Guard has the National Guard Drill Sergeant Program to support the RSP (Recruit Sustainment Program). The hard part is getting an AGR position. Go the this website for more detailed info on the ARNG DS program. http://www.virtualarmory.com/ds/
The POC is at the bottom. Hope this guides you in the right direction.
BTW, I'm a 79T (National Guard Recuiter) so I recruit during the week and I'm a Drill Sergeant on drill weekends for the soldiers my team recruits unitl they ship to BCT. Its a very unique opportunity. Good luck.