I do a lot of smoked oysters and steamer clams. Never tried razors, but they sound great. For steamers and oysters, I steam them open in a big pot with a little water. Makes it much easier than cleaning them raw, they fall out of the shell. I think it helps a lot to have them cooked before you smoke them. – Firms them up and gets a lot of the water out of them. Then I soak them in Yoshitas or make my own brine with brown sugar, sesame oil, soy, garlic, etc. An hour or two in the brine is enough. Put them in the smoker for an hour or so on a rack oiled with olive oil until they are done. Brush with a little oil, pull them out, let them cool, and bag them up. Very simple.
You can also start with leftover steamers – I keep a bag in the freezer so that I can whip out a batch of smoked clams whenever I want.