There aren't many free lunches, but you can make a pretty good sandwich with a couple of ingredients that complement each other.

The key to getting it to work just might be a good sucking exhaust hole or two aft on the fuselage. Place a decent vent or two in a good strong negative pressure area to start. Make sure there aren't any significant openings from there forward to the hole in the cowl behind the prop, and you might have a winner. Negative pressure right behind the spinner could make the holes in the spinner work. Just having holes in the spinner aren't going to insure much of anything.

A number of designers in WWII tried to boost engine cooling with a focus on the area of the spinner and immediately behind it. There were a couple that worked. One used an impeller immediately behind the prop. Most helped the cooling, but took horsepower. So they settled on pressure cowls. Which should be a clue as to what makes cooling up front work. Pressure cowls work great. And depend on having negative pressure to get the parade started.

You get the negative pressure back at the exhaust holes and contain it all the way to a hole in the cowl right under the spinner. So the spinner backplate feels negative pressure that it exists thanks to those remote holes.

Good thing about working negative pressure for your purpose is the simplicity. All you need to get results is a hole or two. Pretty low maintenance too.