Question How do I properly use a can of compressed air to clean my laptop?

[CYB3RUN0]

I own a Toshiba satellite L740 and I would like to know how to use a can of compressed air to properly clean the dust out of it, I have manually taken the laptop apart to clean the fan by had, ie using qtips with a little alcohol to clean the blades and casing but that didn't seem to fix the problem of it overheating and shutting down, any tips or help would be greatly appreciated
Edit: the reasoning for doing this is because the laptop randomly shuts down but only during videos or loading screens for games

 

[CountMike]

You better check and change paste or thermal pads under the heat sinks. With manual cleaning you have already done better job than an compressed air can can do.

 

[CYB3RUN0]

Thanks is thermal paste expensive? Cause it seems like whatever remains of what the laptop had, in terms of thermal paste it mostly gone and it was a grey colour idk if that's normal or not though