Dang am I jealous. Of all my AK trips, Kodiak in September for silvers is my favorite. Done it 3 times now, and can't wait to get back again.
The great thing about silvers - you're not matching a hatch or any such nonsense. Just trying to get their attention. Big flashy flies in black, hot pink, chartreuse, and metallic silver are all gonna do fine on different days at different times in different spots. Personal faves include egg sucking leech, baker buster, kodiak flash fly (a must), pasagshak (purple and pink), and sometimes I'll keep a few spey-style flies like the fall favorite. Mostly pretty large - 2/0 to 2. I often use longer shank hooks for these flies.
One of the best things about AK silver fishing - you can take a simple travel vise, a handful of gaudy materials and hooks, and tie up just about anything on the spot.
Suggestion for when in Kodiak; rent a cheapo car and drive over the hill and along the coast. The Olds an American rivers can be really productive. And at least once go all the over to Pasagshak. There, especially at low tide, you can catch em right in the surf before they enter the stream ... like this one (who was yummy when cooked that very evening!)
Enjoy!