Phil provided very good, solid info on getting a coho here in the more southern waters. Like Phil, I've found flash and movement to be important. And like him, I've found the amount of flash and how fast you strip the fly is also important. However, there are not set stripping speeds, depth of fly, amount of flash that will work most of the time.
You really need to find a pod of fish and work them with down and across casts followed by stripping the fly back with different retrieve speeds until you get a fish to follow.
I have also found a fly with hot pink or fuschia in it is better than one without. I carry Flash Flies (used to be called Karluk Flash Flies) tied on #2-#6 saltwater hooks in silver Flashabou wing,tail,body with hackle collar in hot pink, purple, hot pink&purple mixed, KF blue, mixed KF blue&purple, and red. Flash Flies with hot pink Flashabou tail with silver body and wing with hot pink or hot pink&purple hackle. Flash Flies with lt blue Flashabou tail, silver body and wing, hot pink or KF blue hackle.
Bunny leeches in fuchia with fuschia Crystal Chenile body with cerise and dark blue Kystal Flash tied at the head so it flows over each side of the body on a #3 AJ hook. And a fly developed by Don Kaas of Port Angeles simply called the Blue & Purple Pheasant: tag, oval silver; body, purple braided mylar; rib, oval silver; hackle, 'blue-phase' ringneck pheasant rump; wing, very light powder blue calf or artic fox (dye calf or artic fox in a very weak dye bath of KF Blue dye to get the color, the color is very light). I use the Blue & Purple Pheasant when the fish have refused all the Flash Flies and the bunny leeches. This one is also fish downstream with a stip retrieve.
Coho are the only pacific salmon I use a single hand rod on because I can cast 70' and then strip back to 20', then do it again with a single backcast. 2-hand rods aren't nearly as nice to use when doing this.