A western deba is double beveled and would be sharpened like any other gyuto.....it's just a thicker version really.
Here is a YouTube channel that I really like. It's mostly in Japanese, but to watch this guy is to learn how to use the knives you're asking about.http://www.youtube.com/user/itasan18
A yanagi (sushi knife) is not really meant to be a sole tool used in fish processing. A deba is used to heavy tasks and much of the fileting. Removing the head, cutting bones, etc. are all much to difficult for the delicate edge of a yanagi to do.....you'd chip the edge horribly if you did.
Sorry about the Shun Pro comment....I thought they were flat backed and not hollow but I seem to have been wrong. *hangs head in shame*