Hand painting with spray paint?
Spray paint, by design is in a pressurized container, to belabor the obvious. When used, the material is converted to an aerosol by the pressure, which then travels some distance at a good speed.

If you are attempting to spray it in a cup, a good portion of that force will result in back-spray, pushing the paint out of the cup. This is undesirable. 

A couple methods can be used to mitigate this problem. One is to use a large container, not a cup, something bucket sized and hold the nozzle near the edge of the bucket. Spray in a direction to cause rotation of the pressure as well as angled slightly downward, to keep the spray in the bucket. A portion of the spray will be wasted by coating the side of the bucket, making this a less than optimum method.

Another option is to find a nozzle from a product using "spray straws" that direct the substance. Common sources are compressed air cans, also known as computer dusters, lubricants such as WD-40 and others. If the nozzle and straw come from such products, be sure to clean the material thoroughly to avoid paint contamination.

A suitable receptacle for this method might be a tall soft drink can or even a wide mouth tallish jar. Position the spray straw in a manner similar to the bucket method, pointing slightly downward and in a rotational manner. You will get some back spray, as the pressure has to go somewhere. You can reduce that problem by spraying under a rag or similar open-weave cloth or through a hole in the fabric.

Spray paint is also more volatile, and you will likely have shorter working time with the paint that collects before it dries or becomes too thick to use.