Twice-a-Day Training Experiences

I was wondering if anyone has had experience with 2-a-days? If so, what kind of split did you use, what did you do in terms of progression, what differences did you have between your two daily sessions, etc? Basically, I’m looking in to doing two-a-day training for the 12 weeks I have of before school next year, since all I’ll be doing is working, and I work at the gym that I train at so I get to eat tons of protein and good food all day.

One last question, which do you think would be better for size: having the AM session be compound and the PM be isolation exercises, OR having the AM be heavy lifting (4-6 reps) and the PM be higher reps (8-12)?

Thanks a lot in advance! I look forward to hearing anyone’s experience!