How the special effects were added in the monsters film

I found a clip on YouTube showing how monsters was made. The film monsters was made by a man called Gareth Edwards in 2010. 


In the clip he shows us how he designed and brought to life the "monsters" in the film. He began by drawing up basic images. These images were then brought to life in some digital clay, which they could be moulded out in. Once they were designed they could add the movement and colours. 


This film had an extremely low budget of $15,000. The way they saved money was by only having two actors and the rest were found on site. For example, they are said to have walked into a petrol station and asked who spoke English, one man stepped forward and he acted in the film. This would've saved money as they didn't have to pay to fly him out or pay for his accommodation.  Also they saved money by not using the highest tech equipment. They are said to have used digital cameras and basic equipment. 


This is the clip. :)
http://www.youtube.com/watch?v=z52OHXfLbSU


This is one example of the special effects used within the film. The big wall seen in this image was added in post production by Gareth himself. 

In the image on the right you can see another example of special effects. The monster was added as well during post production. 

Some examples of things that might be added during post production are, production sound (dialogue), sound track (the music that is played throughout the film is written, performed and recorded, sound effects and visual effects.