Oh, on the homemade can flamers...
If you use the little straws and light the end, you have a self lighting flame thrower for a couple minutes. Risky, though.
WD-40 is what we used when I was a kid. I believe my dad took out a wasp nest that way once. Using the straw, though I don't think he lit the straw.
Its more like the flames on the fire knives, though: a good amount of local heat but it doesn't really stick to anything. Its not a flame thrower with thick fuel that... well, yeah.
It'll startle the hell out of someone, though. Never thought of using one defensively.
I do recall that short bursts are important and you have to full press and full release the spray head: nothing inbetween or you risk the flame traveling back up the slowing stream and into your can. Theoretically. Never had that happen and never knew anyone who did. Either way, you want something that comes out of the can faster than it burns - that is what keeps the flames away from the can.