I vacuum out the area a couple times a year with the shop vac and in the fall used the shop vac and hose to flush the loose gravel.
While the grille screens are good, small debris and gravel will still get in there which will then require bumper removal to clean. Not something I want to do on a regular basis.

 

DIY completed...Just completed a round trip drive up to the lake in 102 Temps. My cars operating water temp 175Deg and Oil temp 220Deg. With the third radiator install, oil temp differential approximately 12 Deg. I am very happy with the addition.