Here is a link to a full video walkthrough of the game on Hardcore with free aim, no golden guns, and full commentary. It should help for any of the difficulties that aren't timed - just bear in mind you will not be able to rely on the painkiller revive. Everything else should stand up.
http://www.youtube.com/playlist?list=PL0D7A1EF88E1D1BAC&...Hope it helps.