The 20 is an excellent gun for its price and size. This gun is good if you are in a cramped environment, and lack the room necessary for a good aim with a 50 to 200. The car that you use is essencial to your success. You will either miss your target completely, or end up hitting someone with your car. Always keep a few towels in the car, as water guns usually leak a bit, and sometimes the wind blows water back into the car.
Random shots are useually less efficient and result in misses and wasted water.
The targets I suggest are jr. Useually, people that have reached this age can take being shot as a joke, which is all that it really is. Next, make sure there aren't any parents around. Most parents or adults have the common sense to take down your liscense plate number, and that is the last thing that you would want to happen. If you do find a good target, always ensure an escape route.