UPDATE – So a friend just turned me on to the fact that you can actually talk to a drive via a raw path in OSX. Using a device name like /dev/rdisk2 bypasses any extra buffer cache in between you and the raw disk. So in the example below, the entire operation would move much faster by using /dev/rdisk2 instead of just /dev/disk2. Thanks to Jared for notifying me of this and superuser.com for explaining!
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Its literally the same as on linux, except for you need to properly unmount making the entire process look something like this:
diskutil list diskutil unmountDisk /dev/disk2 dd if=inputfile.img of=/dev/disk2