Im an a/c engineer by trade, the aerosole cans work but arent very good, the a/c system is a criticaly Charged system and requires an exact amount of refrigerant to work properly.
Most places have offers on ac recharge, although i dont agree with the way some garages do it i would reccommend it over an aerosol, iv done my own so i knew it was recovered, evacuated, purged and recharged properly.
Once its working use it reguraly to keep it working, even in the winter run it for 15 mins a week, this keeps the compressor shaft seal lubricated to prevent it leaking and loosing its gas.