Cleaned and/or replaced fans, and/or replaced screens and/or keyboards,... for at least 6 laptops this past year. A real pain. Laptops are not designed to be disassembled. Some require the screen to be removed. All of them were down to the bits. Not an easy, quick job.
And: the screws are different lengths, thicknesses, color,... And there are always more to replace than I find holes for.
I found lots of dog hair in one. The others were mainly dust from blankets and clothes. I always use a clipboard to support my laptops when used not on a desk.
One had a dead fan. I replaced both of the two fans to know continued joy.
Some use closely spaced fins that accumulate micro debris. This is by design.
If I have to disassemble completely I will clean the chips and heat sinks and apply new compound.
I use a small tankless air compressor to blow dust from computers. Cans of air are too expensive and wasteful. And never contain enough to finish a job. Good for little quick puffs when soldering,...
Remove the DVD drive, remove the battery (should be removed when using AC to increase battery life, and reduce heat from charging), remove all panels, remove the ram, use the air compressor to blow thru all the holes. Use a small, long bristled brush to push thru the fan vent holes. Blow again.
If you need to disassemble, find the service manual on line, and search and watch a bunch of videos before you start. Remove enough screws to remove the keyboard. CAREFUL with the ribbon connector. These can break easily if the wrong technique is used to open them. Some flip, some slide. Use a bright light and a magnifying glass to see clearly. Blow thru the revealed holes. Might not need to do more. If so, remove next part, and clean again.
Keep the different screws in different containers and locations on your work surface. Make notes about the different screws.
I have an 18 inch laptop on my desk that is often running videos. The fan cycles lots when doing this. Not so much when recording