Just wanted to through this in here too. This is the video that I watched when I started working on mine. It has a lot of good info as far as installing fastboot and using it. All he needs to do is replace CWM with TWRP and it's commands.
How to: Root ASUS TF300 + CWM Recovery (Works on ALL Firmware) - YouTube
Like I mentioned earlier, my tab is running JB. The ICS bootloader is a little bit different. I wish I could be more help but I'm not up to speed on ICS.