One at a time so you do not cross the ingnition wires.
I do mobile auto repair and there is no clear cut tools that always work for all cars, I have many different tools to make the job easier for all the different cars I work on.
Differet lengths of extensions,
Universal Swivels and/or CV Joint Swivels (yes there are CV joint swivels for ratchets)
Different types of ratchets (flex head, swivel head, multi bend, long handle, short handle, I even have one that by twisting the handel you can rotate the socket)
And proper sized sparkplug socket.