Both are correct. The Scenic Cement that is included with the Grand Valley Layout Kit is a concentrated formula and does not contain the wetting agent that regular Scenic Cement does. This is why the Grand Valley (and other Layout Kits) instructions state to mist Ballast with "wet water" before applying the diluted Scenic Cement.
Ballast is placed along the railroad track to model actual ballast that holds track in place.
Talus is used to model rock debris under rock outcroppings, rocky hillsides or embankments.
If you are just adding landscape materials, such as Ballast, there is no need to scrape the turf off prior to application.
If you are laying track and adding Ballast, we recommend scraping the turf off before adhering the track.