Agreed.
On the following thread, I've done 1-step correction on a silver Ford Focus prior coating application. The swirls and paint stains were not much visible away from direct sunlight, but if I'm to apply a coating, I will do my best to leave an optimum underlying for it to adhere and protect.
http://www.autogeekonline.net/forum/show-n-shine/76044-2010-ford-focus-pbl-surface-coating.html
Hope this example helps you deciding on what's best for your case.
Should I add the best protection (actually a coating) to my swirls and stains, or to my flawless just polished paint?
Another suggestion is, if you don't have the full time for the work now, just use a cleaner wax.
Car will be protected and paint will be cleaner while you find enough time for whole coating process. You can also top your cleaner wax with another dedicated protection of your choice, just follow product guidelines to respect 'cure time' between applications.
Here on this Peugeot I've done exactly this:
http://www.autogeekonline.net/forum/show-n-shine/75723-360-aio-transformation-peugeot.html
Owner wanted his car looking nice and a coating, but (on that occasion) couldn't left the car the time needed for whole coating process.
I've washed, clayed, and used XMT360. Car went back to well maintained state. This car is scheduled for next week for the coating application.
I'll save time on claying, because car has been clayed recently. I'll do 1-step correction/polishing like with the Focus cited above. Then, I'll apply the coating.
Remember! All my words are suggestions to help you find the best for you, not 'The Right or Best' way to do it. It's up to you to read mine and many other opinions to form yours.
Hope I've helped,
Kind Regards.