My preferred method is to take a strong fan and put it inside a cardboard box with a hole cut just big enough for the fan to eject air from the box and make a vacuum. Then you simply need one filter big enough to cover the top of the box, not four filters, it still works great!

Squirrel cage style fans are typically going to be more effective at making a pressure differential too just because of the shape. A good strong floor fan, the kind for drying out puddles, is absolutely fantastic for this.

Beyond that a good N95 mask will do wonders for making life more bearable while out in public! They really do manage to scrub out a lot of the particulates if you get a good fit and they come in cool colors these days.

Here's the standard Corsi-Rosenthal box instrucrions: https://corsirosenthalfoundation.org/instructions/

There's no need for 2" filters. 1" works fine to filter a large room with the standard box fan in several minutes. That's also what the standard guide recommends. Couple of days ago at the peak smoke in Toronto it got the PM2.5 from 50 to 0 in under 10 minutes.

I wish filter media wasn't so fucking expensive