I used to use a 50 gall oil drum for hot smoking mackerel, but for trout - 4 or 5 at a time instead of 40 or 50 - I've been using my Weber grill, set up like this:
http://www.bluesmoke-bbq.com/037spli...plit_grill.php
I like to smoke them with the skins on (I gut and top-and-tail them to fit), as the more bitter tastes from smoking are then on the skin and a very small surface area of meat.
It's imperative to brine the fish: 80% solution is about a pound and a quarter of salt in 4 pints of water, and this will salt up to 10 trout (in two 'sittings' - I use a washing up bowl, put 4-5 trout in, place a board on top and weight it to keep the fish submerged. After an hour or so I smoke them, and brine the second lot if I'm doing more than 5).
I don't like them too salty, so I score the thickest part of the meat and brine for about an hour and a quarter for (what started out as) 2-3lb fish. Dry them thoroughly and cook smoke for an hour or so - make sure that the thickest part of the meat reaches 140 degrees F (I use a Weber meat thermometer).
This is a Juancho's Smoked Trout page:
http://www.bluesmoke-bbq.com/064_gri...oked_trout.php
He does a dry rub, otherwise we agree....
I use lumps of hardwood (ash, atm, as I have some), and the Weber air in/out system means that the heat and smoke is pretty controllable - just takes a bit of practice. Yum...
Works for me (and the suddenly many friends who like smoked trout...

).
HTH
Paul