Out of all the methods that I have tried on the Squamish River and its tributaries, the most productive one involves a small piece of chartreuse/bright green wool under the float. The rigging is similar to what you would do for coho salmon on the Chilliwack River, by adjusting the float depth so it is at least 1 to 2 feet off the river bed. This especially works great when the water has a bit of colour to it. For bright sunny day and clear water condition, use a piece of darker coloured green wool. Slow drift the float close to shore and watch out for the sudden strong takes. If your float is bobbing up and down as it drifts downstream, then the float depth needs to be shorter. The method does not guarantee catches of fresh fish, as chum salmon of all stages in the river will bite readily.
Spoons have worked in the past but I find that they do not work as well as the above setup. Spoons are what I use when I wish to selectively fish for coho salmon because I find most of the fish that go for them are coho salmon.
Again, keep the retrieving speed fast enough so the spoon works through the water column above all the fish, so you won't be foul hooking chum salmon on their backs.