STEPS:

1. Affix the bottle cap to the soldering iron

Must precede step II. Here’s the basic idea:

Iron —
________|\_____ Cord | | Wide-mouth
Before [________| _____|======= | | cap
|/ | |
--- (top)

Iron ---
_______| |____ Cord
After [_______| |____|=======
| |
---

Get it? When you screw the cap back on, the heating element will be enclosed in the bottle. This is the part that makes it important for the handle to be at least 1/4" narrower than the bottleneck. The base of the shaft will get rather warm; the soda bottle is not made of high-temp plastic like the iron's handle, and releases toxic fumes (and eventually melts) when it gets hot, so it's important that they don't touch. Anyway, just cut a hole in the cap large enough for most of the handle to fit through. A rubber grip on the soldering iron makes a nice tight seal with this hole. Use tape to close any opening at the bottom of the handle where the cord enters (the expanding air in the bottle will force vapor out of this hole).

Eager to try your vaporizer? Skip to step V and be prepared to plug and unplug the iron frequently during use to keep the temp. down (or plug it into a power strip with a switch). Leaving it on continuously will heat the plastic bottle too much; leaving it on and lying it on its side will quickly melt the side of the bottle, make a big smoky plastic mess, and possibly start a fire (see disclaimer).
2. Wiring the dimmer switch and soldering iron together

_________
[ Dimmer ] (not to
[ Switch ] scale)
from [_________] Plug
soldering || ___
iron / \ / |____
———————–/ \———————[ |
--------------------------------------------------[ |____
\___|

This crude ascii diagram is intended to demonstrate the wiring of the dimmer switch into one of the soldering iron cord's two lines. I suppose this requires minimal wiring skills (but not necessarily experience). Use a knife to separate about 2" of the two wires in the cord. I did this about 4" from the plug, leaving lots of cord between the dimmer and the iron; eventually I plugged my switch box into an extension cord rather than squatting next to a wall socket. Make sure you don't expose the wire on the side you won't be cutting. Now cut one wire and strip about 1/2" down both sides. Use the screw-down connectors included with the dimmer to join its wires to the cord (just twist the two wires together and screw the connector down hard). Wrap the connections in plastic tape to be safe.
3. Housing the dimmer switch

I just cut a hole in one side of a plastic 10-disk 3.5" floppy case large enough for the little metal rotor in the rotary dimmer switch to fit through and bolted the dimmer to the case. It went in diagonally. No drill? Make the holes for the bolts by driving a wood screw through the plastic. Mark "off" and "max" settings and adorn to taste.
4. Attaching the thermometer

_
_|_|_
| | This is supposed to show a slim, high-temp thermometer
| | | attached to the shaft of the iron. Attach it with wire
| | | (strip the paper off a bag tie). The thermometer must
| o | contact the iron as tightly as possible and must include
----- the range 150-250 Celcius or so.
___|_|___
\ / I have not accomplished this yet - all the oven therms.
\ / I have found are far too large for the task.
| |

5. Soft drink bottle ---> vapor chamber

The bottom of your bottle will be the top of the vapor chamber. Cut a roughly 1/2" diameter hole near the bottom of the bottle, and cut a smaller hole for air intake near the neck. Voila.
6. Assembly and usage

Here's another crude ascii drawing to illustrate the whole setup:

_____
/ O \ Pack the hollow space in the shaft of the iron with
| | your favorite hemp product. Buds are best chopped into
| ~ | small bits. For use with hash, consider filling all
| ~ | but the top 1/2" of the shaft with aluminum foil.
| ~ | If you're forced to fashion a bowl on a nonremovable
| ~ | tip, make sure it fits in the mouth and resists
| o H | spillage, and realize only material very very close to
\ H / a hot surface will vaporize (huge, stuffed bowls won't
\_H_/ work right).
[___]
| | Dimmer Box
|_| ___[_]___ extension cord socket
\__________________| |__[=[————————-[=
|_________|

Screw the cap down and power up! Keep both holes covered with your fingers and wait about 1 minute. Put the dimmer on full at first to get up to the working temp. Turn the switch down some when you see first see white vapor rising from the bowl. Unless you’ve got the thermometer, finding the right dimmer setting to vaporize without combustion will take several trials :> . If you do have it, a reminder: shoot for 200 Celcius.

Allow a decent cloud of vapor to form before putting your mouth to the top hole, release the carb (bottom hole) and inhale! Ahhh.