You can use any color of grays that you like, I tend to use the "C's" but neutral and warm grays will work just fine. For this image I'm using C1, C3, C5, C7, C9 and 0 (Colorless blender). Ignore the 110, I didn't end up using it :0)
Last step and finished image!
Used the finished image on this card so you can see how it looks :0)
Image by The Greeting Farm (Oliver and Amelia "Journey" set)