Aerosol

Aerosol propellants come in cans, you can buy them at wal*mart, and they do not need any auxillary hardware (like a fuel meter) to use. As such, they are quite popular.

It is recommended that you avoid using hairspray, as it will gum up your chamber. Deoderant is much better - the generaly recommended one is "right guard" in the brown can, although any spray with flammable propellants will work (check for things like propane, butane, isobutane and/or ether). Many dislike the smell of "burnt flowers".

Because the amount of fuel cannot be measured accurately (the usual procedure is timing the spray duration by feel), it does not yield the performance that metered propane does - the pressure generated during a closed chamber firing is estimated to about 30-40 psi, as compared to 40-50. If your cannon is not firing, or is firing weakly and you have a flamable fuel (verified by spraying over a flame): check the ignition source. If you are getting a spark, you are most likely spraying too much fuel in; play around with how much you spray in until you get a good bang. (and remember to vent your chamber between shots)