"I felt an intense sense of connection but it was like opening a Pandora's box."
At the start of the journey, the celebrities spat into a test tube, which was sent to the United States for DNA analysis. The results were then matched to a worldwide database.
During the series, hosted by Rocky Horror Picture Show co-writer Richard O'Brien - participants are not told where in the world they are going to until they turn up at the airport and are handed their DNA secrets.
Billing's adventures will be screened on October 21, along with Sam Wallace's story.
Wallace discovers his ancestors were from England but records stop before freedom fighter William "Braveheart" Wallace fought for Scotland in the late 13th century.
A DNA test is the only way to find out for sure if his descendants once stood on the battlefields of Scotland and the results throw a couple of curve balls at him to deal with.
Billing, 38, grew up in Masterton. She discovered family links going back more than 15,000 years.
"I knew I had British blood and my grandfather used to kid me on I was part Spanish," she said. "But through my DNA I found connections to ancient people and tribes in far away countries that blew me away. All this came about from me spitting into a vial and I am now very curious to find out more about my past. It was an incredible gift to be given and the intensity hasn't diminished since I came back to New Zealand."
• The DNA Detectives 8.30pm October 14 on TV One.