If the coating was applied to a car that is a garage queen about 9 months ago, can it simply be reapplied now without doing any type of clay barring or polishing?
Get the car clean - however you would do this - wash/wipe. Then feel paint softly with sandwich baggie. The paint should fee smooth. If so, wipe surface with panel wipe and re-coat.
I would suggest doing JUST a section, for example half the trunk lid and then wait a day or two and inspect. If all looks good - continue to the rest of the car. If something isn't right - you'll be glad you only did a small section.
Make sense?
Coatings - better protection but trickier to work with over time on vehicles/boats.