Here you can see the dull point being used to bring out the detail in the grille. Just a little gentle pressure will do.  The Heavy Duty aluminum foil is tough but be careful. You can tear it if you go at it too hard. (You did get the Heavy stuff right?) This is why I like the old Buicks.  What a distinctive grille, and the detail available on the Alloy Forms model makes it easy to duplicate like this.