Soak them, loosely wrap in foil, poke 3-4 dime size holes on the top. Put on one side of your grill (or over one burner) with the fire on low depending on your grill.
Put whatever your smoking on the other side of the grill with no fire "indirect cooking". And don't open the lid for at least 2-3 hours, keep the smoke in the grill!!!
This should get you started, but there's no "fool proof way to smoke on a grill because every grill is different.
Trial and error is a must, so do a couple runs with store bought Jalapenos first.
You don't want to ruin your Douglahs right off the bat...
Good Luck!