You can paint your car bumper without having to rent an expensive air gun and find room in a rental paint shop. There are spray paint cans specifically designed for use on car parts that you can use for this purpose. Remember to use newspaper to protect the other parts of your car before you begin painting. The special paint for cars has a coating element in it that protects your paint and car from the elements.
Paint in layers. Do not expect to get it completely coated with one layer; it will take several layers to get the right look. Remember to keep moving your spray paint can in a uniform manner to prevent dripping and running paint.