Are you shooting "Shutter Priority"? Your camera should synch with your 580EX at 1/250s if you have it set at E-TTL. If you set the flash to manual, you can get a little more creative, but you'll probably need a light meter. I use a Sekonic L358 and it works great. It also has a transmitter module that allows it to trigger Pocketwizards if you get into studio work. A company called "Blue Crane" makes a tutorial DVD for the 580EX II that might be helpful for you -http://www.bluecranedigital.com/580EXII.htm
I'm not familiar with the MR-14EX so can't offer any help with that one, sorry. Dalantech is our macro guru and I'm sure he's familiar with it and could offer some advise. He has a number of tutorials on his site that might cover it.
Here's a link to his blog: http://nocroppingzone.blogspot.com/