How do you replace a thermal release device in a gas hot water tank?

Turn main water off --> drain water below device --> remove old device --> use pipe dope or teflon tape on new device before installing --> install new device --> turn water back on

It's below the Burner, You do Not need to drain water. Mine shut off the air supply to the Burner by closing the air damper! DTE Big Fail!

I am looking for a tool to compress the metal rod that pushes the damper open, any suggestions? I tore up my forearms trying by hand...