Several years ago I bought an offset smoker - looks like the Brinkman
Silver - thing as it came was worthless. Some of the necessary mods
a

sealing up air leaks with wood stove gasket material and high temp
caulk

close up the smoke stack - cut a new one -4" -at the end in the bottom
of the smoke chamber

Add a heavy baffle just under the grill racks to increase mass and make
the temp more stable. I used a 1/2" thick sheet of steel which just
fit under the grill and also blocked the heat and smoke from the offset
burner from coming directly intothe chamber - it has to go most of the
way down the chamber before rising into thte top of the smoke chamber.

Block off the smoke stack opening so that the smoke and heat must go up
into the smoke chamber and come down before exiting.

Cover the smoke chamber with at least 6" of fiberglass insulation - use
unfaced insulation and then on top - use aluminum duct insulation to
hold it on. The insulation is held in place by 1/2" x 3/16" steel
strips bolted onto the body of the smoke chamber. What this does is
let you smoke year round and in a lot of wind and not use much fuel.
Takes maybe 4 or 5 sticks of oak to smoke for 10-12 hours.

All of the info on how to do this was obtained off this site - be
careful in measuring for the steel plate - it has to butt up against
the firebox end and be very close to both sides and maybe 3" from the
end away from the fire box. Get to the Klose site - use their smoke
recirculation technique as a guide. If you like things really smoky -
adding the insulation really reduces the amount of wood you use - and
the smoke flavor is not as strong - but good enough for me - really
perfect for smoking whole salmon and brisket.