For the most part I apply my sealants and waxes with my Porter Cable 7424 polisher using a blue or red foam pad on speed 3. Applying either product in this fashion guarantees a more uniform or more consistent coat therefore using more of the product efficiently..
When I do need to apply a fine wax I'll use a foam pad similar to the ones offered by Pinnacle...
If you are leaving behind scratches, either the applicator you are using is dirty or the car is not clean and in the process you are moving dirt particles around which is scratching the paint. While I use my pc now, when I did it by hand, a clean microfiber pad or foam pad both worked fine.
YES I clayed bared first. I did back and forth as the wind would blow over it. Maybe I am just to picky, only notice scratches under flourescent lights.