--This is how "grey-shirting" works:
A player commits to a team that is over-signed.
Said player does NOT go to school in the fall OR can enroll part-time and pays for his schooling himself.
Said player is NOT officially on the team.
In January, said player enrolls full-time and offically joins the team. (Player now is a recruit of next year--in Trent's case he will be a member of the recruit class of 2012.)
Once a "grey-shirt" joins the team offically the player has a 5 year window and still has the ability to red-shirt if they choose.
As a "grey-shirt" a signee can not practice nor condition with the team, cannot be given any advantage not given to the general student body. "Grey-shirts" are not allowed to attend team meetings or functions.