First grab the mesh pattern and copy and paste it onto the image (I'm far too kind.. you can use this on your cars!)
Got to the layers box in the bottom right hand corner, and set the transparency to around 50%. Then move the mesh over the grille.
Then, using the eraser tool (E), thn rub out the bits you just don't want! Just like this.... =DYou can use different size brushes to rub out the bits of mesh on the thinner parts of the bumper. Adjust the opacity if you feel it necessary! I like to rub out the bits where there would be shadow, eg, the bits under the vents. Finished!