You can used compressed air to blow out the exhaust ports. I did this last week for the first time on my laptop. I can't say that it got all of the dust out, but a lot did come out. I'm sure it helped some.

Hi, i think it would void you warranty, but if you are up for it it is simple, you just remove the keyboard (there is a yotube video on how to do it, did it myself and was very easy). After removing the keyboard you have some acces to the fan and the fins, so with some care and compressed air you should be ok to go. (the pictures are from my notebook, wanted to check for dust, too)

This is the youtube video i used as a guide (not my video tho). https://www.youtube.com/watch?v=Y0dkQ4rajyM