spraying gel coat for mold

Hey guys im wondering if anyone can help me out on how to spray Gel Coat for the first layer of making a mold.

RIght now I don't have air tools so I can't use an air gun to spray it. I was watching a youtube video on making a mold and it sayis "a cleaning gun is a cheap way for spraying gelcoat".  WHat im wondering is: is a cleaning gun he is talking about literally an empty windex bottle(well one like it) or is that a special type of air gun needing an air compressor? Here is the youtube link to what i was talkign about. at 1 minute 48 seconds is where hes spraying the gelcoat. https://youtube.com/watch?v=nsvgaWHPMF4

Soon I might be able to get a compressor soon but not too soon. 

So overall my question is, what did he mean by a cleaning gun and is there any way to apply it to an interior part without using an air compressor powered spray gun? thanks!

That's an air gun. There is the Airless spray gun, but I do not recommend them because of the high overspray and large volume waste for most projects. A lot of it goes to waste when using the airless. Air guns, particularly HVLPs use a lower velocity and a more controlled spray resulting in very little waste and a LOT more control.

A Cleaning gun is a bit of both worlds. Dirt cheap, don't need a powerful compressor, and relatively easy to clean and maintain (Assuming you don't let the material cure inside the gun itself. But if you do, you only out about $15) It's kick back is that it is not as efficient and controlled as the HVLP, but for most smaller applications, it is fine for spraying on most mediums for molding.