How much dirt could really be in there?

That looks cool, but I have tried to pull the vents out of the front bumper, but I could not do it. Is there some sort of trick to it? Does anyone have directions or is it even possible to do without taking off your bumper? If I can do it without taking off the bumper I will definately do it and put mesh behind there (also but a black gloss paint of the vents themselves).