Did the Dawn wash, and Z1-Z2-Z2 treatment last fall. Should I wash with Dawn again now that it's Spring before polishing again, or is just the usual Z7 wash good enough to prep it for the next couple coats of polish?

 

The Dawn was a one-time, initial-prep thing to remove carnauba wax and oils. Every six months, you should use the Z-1/Z-2. Then, Just wash and Z-2, wash and Z-2, wash and Z-2 to your heart's content.