I used to buy dust cans from office supply stores. They have a limited amount of quantity per can and the cost per purchase over the long run isn't what anyone likes. I recommend that you purchase the Metro Datavac Electric Duster ED500. I bought on ebay for $50 and blows 70CFM (it is 20CFM less than an air compressor for power tools, but still very powerful enough blowing stuff off without damaging equipment). It is specifically designed to blow dust from the surfaces of electronics (TV, A/V receiver, Computer, LCD screen, ect). Better than canned air, which sometimes doesn't blow all the dust out and using 92% Isopropyl Alcohol to remove what is left (which i done before) isn't ideal.
Here is a link to amazon if you are interested:
http/www.amazon.com/Metro-Vacuum-ED500-500-Watt-Electric/dp/B001J4ZOAW/ref=sr_1_1?s=electronics&ie=UTF8&qid=1356065425&sr=1-1&keywords=datavac+ed500
I saw a picture of the Asus K53E on newegg. Looking what appears to be exhaust port toward the side where you plug the VGA port and the intake vent holes appear on the underside center and underside front. They look small and narrow. Get a single print paper and cover the vent, if there is force holding the paper than that is the intake, if it pushes away from the laptop then that is the exhaust. Appropriate the small fan toward the intake vent, if you were mistaken.
I have the Cooler Master U3 Notebook cooler and i have the fans position to each vent hole for cooling. Usually laptop cooling pads drop only 3-5 degrees Celsius at most, sometimes only 1 degree.
A link if you are interested:
http
/www.cmstore-usa.com/notepal-u3-notebook-cooler-refurbished/
The cheap way is just elevate your laptop with a book without covering the vents underneath.
Asus advertises IceCool Technology which just means that the hot components like gpu and cpu are facing toward the floor and other cooler components are facing toward the keyboard. The motherboard has two sides.
Hope this helps.