macos - How do you create a bootable partition on a USB drive?

I have a bootable ISO designed to be burned to a double-layer DVD. I don't have a double layer DVD burner, so I would like to stick the ISO image on a 50 GB partition on a USB hard drive I have. How do I get the boot info onto the hard drive?

Attempt 1:

1. booted into Ubuntu 9.04 LiveCD


2. deleted the partition on my existing USB hard drive


3. sudo dd if=/path/to/image.iso of=/dev/MyUSB


4. booted to USB drive


5. error: Error Loading OS

Atempt 2:

1. booted into Ubuntu 9.04 LiveCD


2. deleted the partition on my existing USB hard drive


3. sudo mkdosfs -I -v -n iPC /dev/MyUSB


4. sudo syslinux /dev/MyUSB


5. sudo dd if=/path/to/image.iso of=/dev/MyUSB


6. booted to USB drive


7. error: Selected boot device not available - strike F1 to retry boot, F2 for setup utility