Games Workshop Citadel Spray Gun - An Amazing Tool or Lame Duck?

Citadel Spray Gun.

So here it is, the Citadel Spray Gun, according to Games Workshop "The cool hand flamer shape hides a robust, highly effective tool that is great for base coating large numbers of models at once. It can even be used with the new range of Citadel Washes for batch-shading." and at just £18.50 it at first seems to be a bargain, but hold on what power source is needed to propel the paint from the jar to your model, ah here it is, a can of propellant.
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