Use about 3/4 lb of headless, shell on shrimp per serving.
Obtain Jerk seasoning from store or make your own - I get a recipe from a Jamaican cookbook which I do not have with me at this time. The seasoning is mostly brown sugar, "allspice" and cayenne pepper. Use about 1/4 cup of seasoning per serving or so - the spice does not penetrate the shells very well so don't worry about overseasoning.
Rinse shrimp. Dredge shrimp in spice or shake in bag till well covered with spice. Place on seafood grille or wire mesh, and place on racks. It takes several grilles to do a mess of shrimp. I try to leave space between them for even smoking and heating.
Add wood to suit taste but a medium size chunk in a Smokete with 3 to 4 lbs shrimp should be plenty.