Try cleaning with the one that is easily removable first, if you can't reach what you need to clean then go further. Use whatever you need to to keep the fan from spinning, if the fan is exposed which it will need to be to clean properly, just holding it with your finger while you spray will work fine. Also cleaning the edges of the fan blades is key as well. When the dust collects on the edge it reduces the amount of air the fan can push, making it work harder. The air itself won't get all of that off, so a dry cloth, or small brush of some sort can be used to clean the edges of the fan blades, though I think a full disassemble may be needed to reach the fans, but I'm not totally sure as I am unfamiliar with your laptop.
If you are going to use compressed air to clean the fans, make sure to hold them in place when you do. The compressed air can will spin the fan MUCH faster than it is supposed to, and may damage the motor on the fan. Blowing the air in the vents will just blow whatever dust that has accumulated into the enclosure itself, it won't remove it. The best way to clean out the inside of a computer is to remove the panel altogether and make sure the dust leaves the enclosure. Just be gentle and you should be fine I'd try removing the panel only at first, if you can't reach the parts that are the dirtiest, or you aren't able to control the spin of the fans, you may need to disassemble, which may cause warranty problems if you have to break a seal.