Step 1: Getchyer Materials
Heat shrink tubing
Piezo igniter from an old fireplace lighter
Pointy pokey thing
Something that will heat-shrink the heat-shrink
A side note: there is another Instructable now by Geoffrito about how to remove the ignitor. You don't need to add extensions unless you want to, just extracting the piezo igniter should give you enough length.
Step 2: Puncture the Lid
I drilled a small pilot hole, then carved out the rest with an X-acto knife. You could also drill the whole thing or stab it with a hot nail, I don't really care. It's your film canister.
Step 3: Add Wiring
Step 4: Shoot Things
A quick note on fuel: Experiment! I used aerosol hairspray, which is very flammable and comes out in a nice mist. That mist part is the most important. If you just dribble in fuel, it probably won't fire.