Reddit reviews Bonus - Includes 3 Extra Filters - Metro DataVac Electric Duster - 500-Watt Motor - Model ED500P Computer - Electronics Duster- Made In The USA

buy a datavac.
expensive but worth it.

as others said hold the fans when blowing air on it.

https://www.amazon.com/Bonus-Electric-500-Watt-Computer-Electronics/dp/B071LQSXGD/ref=sr_1_1?s=electronics&ie=UTF8&qid=1527177507&sr=1-1&keywords=datavac
(Ive had other cheaper ones similar to this and this easily takes he cake. Solid built and 5 year warranty on the motor)

No matter what, you're going to make a mess. Might as well take a load of PCs outside. Get the client to let you shut them down to do this properly. Use the blower below. That little guy is wicked good.

https://smile.amazon.com/Bonus-Electric-500-Watt-Computer-Electronics/dp/B071LQSXGD?ref_=ast_bbp_dp

https://www.amazon.com/Bonus-Electric-500-Watt-Computer-Electronics/dp/B071LQSXGD/ref=sr_1_1?keywords=datavac&qid=1570030380&s=gateway&sr=8-1

No need for an air compressor. Just buy a data vac (which does not vac but blows). If you do get a compressor get a good quality water trap for it. That's really too much pressure though IMO and the data vac is the best one time purchase.

There are electronics dusters that don't create static. There are cheaper ones too, this is just the one I have.

Electronics blowers are definitely a thing but they're pretty damned pricey. I used them all the time when I did production tech work.

Don’t spend money on air cans. Get a DataVac blower. I love mine and haven’t had to buy compressed air since.

Non-affiliate Amazon link:

Bonus - Includes 3 Extra Filters - Metro DataVac Electric Duster - 500-Watt Motor - Model ED500P Computer - Electronics Duster- Made In The USA https://www.amazon.com/dp/B071LQSXGD/ref=cm_sw_r_cp_api_i_H-a6Cb31MZB5X

I don't want you to harm your PC, cuz one wrong move and you could damage something which could cost you a lot of money. I've never used that product but this is what I use and it kicks ass. I know that you were looking at that one for $20 but if you have the money I highly recommend the datavac. It's corded so you don't have to worry about refill or some kind of battery and it comes with attachments hope this helps
It is $75 bucks but i think its a pretty good deal. Most value packs for canned air is about 20 bucks so after a while are we spending that money anyways
Hope this helps

https://www.amazon.com/Bonus-Electric-500-Watt-Computer-Electronics/dp/B071LQSXGD/ref=mp_s_a_1_2?ie=UTF8&qid=1539072665&sr=8-2&pi=AC_SX236_SY340_FMwebp_QL65&keywords=data+vac+computer+duster&dpPl=1&dpID=414T74fJIRL&ref=plSrch

A single can of air isn't going to cut it for this mess. What he needs is this. I have one of these. Never have to spend money on a can of air again. One of the best purchases I ever made.

Forget that. Get one of these instead and never look back. They're amazing.

EDIT: the other problem with air compressors is that they can get moisture in them, and unintentionally blowing a fine mist all over the inside of your PC generally is a bad idea.

https://www.amazon.com/Bonus-Electric-500-Watt-Computer-Electronics/dp/B071LQSXGD/

Link for the uninformed.