Move db from sql 2005 to 2012 with minimum downtime

Hi!

We need to move a 300gb sql db from a 2005 server to a 2012 server.

The database is in simple rec mode.

It exist only in Prod env.. :/

Downtime is allowed, but I would like to get some thought about the method to do this with minimum downtime.

I tried with a backup/restore, and I guess you understand already, it took about 8 hours until the db was restored .. :P

Thanks in advance.