First, while playing ddr definitely helps with ffr- the timing and such- ffr wouldn't help with ddr. The body movements have to be learned separately. Second, skill at ffr, I've found, has more to do with how often you've played fast-paced video games to get that eye-hand coordination up to speed. DDR has nothing to do with that. EVERYONE starts off sucking, whereas I found- and I tried it out on my equally game playing freak of a little brother- I had a natural ease for playing ffr because my eye-hand coordination is so well-trained. Besides, playing DDR with the controller is often harder.

BTW, it's easy to hit two buttons at the same time on the Playstion controllers- both the arrow keys and the buttons are the arrows on the screen, work one with one thumb, and one with the other.