Switching MOS to 12B, how does the reclassing process go? Full OSUT or just the AIT Portion?

As I have experience in this particular realm, here is what I can tell you. Of course, bear in mind that my experience was in 1996, so take that with a grain of salt.

You may very well show up about 1 week before (probably no more than 2 weeks) prior to their BCT graduation. This literally happened to me. You will be on Prior Service Status. If there are separate barracks available nowadays for PS, that is where you may be housed. However, you may also be housed in the same barracks as them....just down the hall away from them. You would do PRT and POI training with them. After POI time, that is your time. When I reclassed to 12B, we were allowed to come and go as we pleased during off hours and weekends. We had to keep the Drill Sergeants appraised of our plans, of course. We also sought their permission for our movements. Better to be safe than sorry. At no time did we dare to be out and about after lights out without their knowledge and approval. At not time will you be encouraged to interact with the IET Soldiers other than during PRT/POI time. As you will be falling under TRADOC rules, the last I knew was that no Soldier...regardless of TIS/TIG...will be allowed to consume alcohol. At no time will any PS Soldier be allowed to correct any IET for any infractions they make. You are to note what they did/when they did it and report it to the Drill Sergeants/Cadre. You will probably form up with the other PS in a small squad behind the company and march behind them. You will probably be last to enter the DFAC during chow but moved to the front of the line (to this day I still don't understand that one).

I had to go to Phase I, and a Phase II when I reclassed to 92Y, trained both times with Army Reserve units.

When ai was going thru 12B OSUT, the recluses just showed up during the A.I.T portion.