I'm on the post 9-11 Bill, I thought it was before classes so I can buy books and pay for the classes?
For the For the Post-9/11 GI Bill we pay tuition and fees directly to the school.  Money for books is sent to you at the beginning of the term
can I take classes at 2 schools at the same time if I still have benefits leftover?
Yes, you can take classes at more than one school under the GI Bill if the classes at both schools count toward your degree. Also, the school granting your degree has to consider the classes at the second school to be required in order to get your degree