The car had a small amount of cold air coming out of the vents with the AC on, then I put two cans of freon in it and it seems to have no cold air coming out now. Should I put two more cans in or is their a problem somewhere else?
If just the air volume was low chances are the system is now seriously over-charged. Most systems on newer cars don't even hold two pounds of refrigerant, and two more, if you can even force it in, will likely destroy the compressor. When it's over-charged the liquid turns to vapor and gets cold too far down the line which means under the hood instead of inside the car. If any liquid sloshes into the compressor it will lock up at a minimum and potentially damage it.
There is no way to know how much refrigerant is in the system unless you recover all of it, then pump in a measured amount after drawing it into a vacuum. That's what your mechanic will do to assess the system's performance. If just the air volume is low, that has to do with the fan, a restriction, or mode door actuator not working.