I keep harping on this, but this is a massive regret - sure they were bulky and power hungry, but I would sell a kidney (not necessarily mine) to be able to buy a modern CRT to enjoy my old PS1 light gun games (Pount Blank, Ghoul Panic, Rescue Shot, Time Crisis etc.) again.

Not OP, but own a similarly open-air PC (Thermaltake Core P3).

I bought a Wolfbox MF200 duster on sale off their AliExpress store for ~$50USD; just need to just give it a quick blast every once in a while and it all remains dust free.

Honestly dust management in open frames is significantly less hassle than in closed cases - regardless of positive/negative internal pressure.