Aerosol propellants come in cans, you can buy them at any grocery or department store, 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 leave an undesirable residue in the combustion chamber. Deoderant is much better - "Right Guard" in the brown can was the generally recommended aerosol fuel until recently, when the formula was changed to use a non-combustible propellant. Any spray with flammable propellants will work, look for compounds such as propane, butane, isobutane and/or ether).

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 flammable 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; experiment with varying amounts of fuel until successful results are achieved. And always remember to vent the combustion chamber between successful and unsuccessful ignitions.