The best way to get a proper crust; is with a stone, although you can
get really nice crispy crusts on just the grill grate itself.
For more info on this...see my post of Pizza on the Grill.
For those that have a problem with the pizza sticking to the peel...you
can pre-cook the crust for a minute or two, on the grill or on the stone;
then take it off and add all your toppings and put it back on to cook.
That's even easier than parchment paper.
Check out the link above for pictures and a complete guide to it.