Need help with making a brushless fan into a camping fan.

[Unclejonny]

Been doing some internet searching and I can't find a way to manually control the speed with a brushless radiator fan 3 or 4 wire. I think they have a built in esc. The BMW brushless fans have 2 big wires and 1 little wire going to the fan. Mercedes and others have 2 big wires and 2 little wires. My plan is to make a frame to hold the fan (kind of like a box fan) and have the fully adjustable speed control on top. But I don't know what all I need to control the speed. I have a 12v lithium battery to power it. Any suggestions? I want to do this for the efficiency of the brushless fan and it would push more air too. From what I gathered I think all I need is a low input signal pwm but not sure. And also I wouldn't know how to wire. Any good input would be highly appreciated.
Thanks!!