I have heard and read that sandblasting can warp body panels.

I have to clean my hood, front fenders, and inner fender wells. What can I (vs. someone I would pay as I do not want to send them to someone to work on) do to be sure that the sandblasting does not warp the pieces? Or is this impossible and I just need to pay someone to have them media blasted?

If it is the heat (rather than the shrinkage caused by "micro" peening of the sand particles) that causes the warpage, can I use a bit of water as I am sandblasting by having someone helping spraying a bit with a garden hose?

Help.