Advice for order of operations and retrofitting trashy sleeper case

TrashGoblin

Whattup gammers! I'm putting together a trash build out of a found case and low-budget new and used parts. I could use some advice when it comes to getting the case fan cooling system squared away. I'm working with a no-name mid-tower ATX case from the mid-2000s, and it's in desperate need of life-giving air. I am going to have to pull out the hole saw and bolt in a whole bunch of case fans. And I figure as long as I am breaking out the arts and crafts supplies, I might as well toss a fresh coat of paint on the inside of the case. But I figure to make all this come together, it'd be best to work from the inside out, IE. case mods - case fans / power supply - everything else.

However, before I give my left kidney to Microcenter for fans and controllers, I wanted to make sure I can install and troubleshoot the power supply/ case fans/fan controller/ daisy chain system before installing the rest of the components. Is that a viable order of operations for approaching a retrofitting project?

Am I able to power and control case fans without the rest of the computer? Or do I need to find an alternative temporary power supply solution while troubleshooting cooling the case down?

Can I combine a variety of different new and used pc fans, or are there inherent compatibility issues?

Additionally, is there an effective way to measure the airflow inside the case by volume or pressure?