Well, that won't really work. You can't mount the disk because a blank disk doesn't actually have a filesystem on it. You can't use dd command because writing to a DVD (or CD for that matter) is different from writing to hard disk or flash memory device because DVDs are essentially WORM (write once, read many) devices.
Now, If you knew what you were doing, you could create an ISO image of the DVD you wanted to create and then use a program like cdrecord (or whatever is available for Macs to write to cd/dvd media) to write the ISO to the DVD.
I've actually done the above from a command prompt in Linux, but generally don't any more as there are pretty good programs for Linux now that automate the process.
What you say makes sense. Thanks.