Vacuuming seems to be discouraged by most sources. It's said that the SMD adhesive can age and cause components to be sucked away, and that vacuum cleaners can generate static electricity, which is harmful to electronic components.
A more modern method is using compressed air, either from an electronic compressor with a moisture filter or from a can. However, cans often lack moisture filters, which means you could potentially blow moisture onto your electronics. But wouldn't you blow away the badly glued SMD parts?
Using a soft brush, such as a paintbrush, is also recommended. But some sources caution that the bristles can become charged with static electricity. Some forum users suggest grounding the brush to prevent this.
For heavy dirt, isopropyl alcohol (90% or higher) with cotton swabs is recommended. Of course, stay away from microfiber cloth on the inside, otherwise the static electricity will strike again.
And then there are the more extreme methods, like immersing the computer in oil or using special cleaning sprays designed for servers in data centers.
Heck... How do YOU clean the insides of your PC?
"moisture" is only a problem if you don't let it dry off before applying power. Your circuit boards were washed multiple times before they got to you. In the before time, we'd disassemble our ModelM keyboards and rung the whole thing through a dishwaser.
A more common problem is people not securing the fans on things; you don't want to spin them at compressed air speeds, ain't great for the bearings or the upstream electronics. Who protects their fan power lines with diodes?
If you can, try to reduce dust exposure in the first place by raising the case above the floor, not placing it in a corner, getting an air filter or the like.
Unfortunately products like this cause a disproportionate amount of climate change because of the gas it contains. They really work though and I've seen dust-clogged laptops that were thermally throttling get like new after blowing them out. There is no trouble with moisture because they don't put any moisture into the can to begin with.
I was hoping flouroketone-based products would get on the market but with 3M being in disarray over PFAS threats I don't think they're that excited about the potential.
Personally, I have used an electric air blower called Xpower.
Link: https://xpower.com/shop/a-2-airrow-pro-multipurpose-powered-...
Besides that, I have an air filter in my office which, hopefully, helps with gathering dust.
If you’re feeling adventurous, maybe try submerging the PC in a water tank filled with mineral oil… :P
Unplug. Take it outside, remove side panel, side fan filter, bottom fan filter, any other filter.
Use skewers to make sure the fan cannot spin too highly (which can wreck them)
Use a powered blower like this: https://www.amazon.co.uk/gp/product/B01G1Z0RF0/
Reassemble.