If your asking if you should polish a vehicle that needs claying, the answer is no.
You'll pick up some those contaminents into your pad and instill swirls pretty bad.
If they don't get pulled up, they'll be left on the surface, not giving you a flat surface, which is what gives you shine.
Like Allenk4 said, they're are other tools for mechanical decon beside claying. There are sponges, towels and even DA pads. Making the process alot quicker and easier.