First you want to make sure you're not trying to prepare a fire extinguisher. A normal fire extinguisher usually have big fat hose openings on them because it's meant to completely cover the fire and smother it. Bug sprayers are supposed to have a thinner, more accurate spray, so poison doesn't spray everywhere. Also your looking for a refillable container with a hand pump to build up pressure and in some cases straps to for ease of mobility.The mix is simple, pretty much you are trying to force pressure into a "full" container, but it makes sense that you are going to get paint trying to gush out. In this case use a little more water, because you don't want to gum it up, and it seems to work well, even down to almost a 50/50 ratio depending on the color of paint you're using. Also keep track of how much time it's been sitting with paint in it, else by the time you reach the destination you'll find yourself carrying around a rock for some time.Flat nozzle of some sort, and that's what gives it that calligraphy look.