What are the chances of getting selected for RASP 2 while in AIT for an E6? Or do I have to report to my Duty assignment first?

Unless you're an IET you are attending school TDY enroute and are on assignment right now. You can't just not report to your next assignment, those orders are what is used to fund your training.

RASP2 has an evaluation board before you ever show up for selection. If you don't have any rated time in your MOS, it's unlikely that they will want to bring you on for selection. But if they need an MOS enough, they may be willing to accept you

Current standard operating procedures are that as a SSG or above, you'll go to your first assignment, then apply, or apply ahead of time. Once you get here, you can ask the 75th Ranger Regiment LNO/recruiter.

There is a 75th Recruiter stationed at Fort Huachuca; right across the street from the Thunderbird DFAC. They'll have all the answers you need.