Denis Clive "Denny" Hulme,  (18 June 1936 - 4 October 1992) was a New Zealand racing driver who won the 1967 Formula One World Drivers' Championship for the Brabham team. Between his debut at Monaco in 1965 and his final race in the 1974 US Grand Prix, he started 112 Grand Prix, resulting eight victories and 33 trips to the podium. He also finished third in the overall standing in 1968 and 1972. Hulme showed versatility by dominating the Canadian-American Challenge Cup (Can-Am) for Group 7 sports cars.

After leaving the sport, Hulme led the GPDA (Grand Prix Drivers' Association) for a brief period, but the cut and thrust nature of the post was ill-suited to his gentlemanly nature and he did not fill the post for very long. He then retired to New Zealand, returning to touring cars to race occasionally in the Benson & Hedges 500 race at Pukekohe Park Raceway in the late 1970s first in Chrysler Chargers then later a Volkswagen Golf, partnering Stirling Moss on occasion for the 500 kilometre endurance format.  Hulme began racing regularly again in 1982 with amateur racer Ray Smith, building up a team with the Holden Commodore V8 capable of winning the New Zealand Production Car Series for Group A touring cars in 1983/84. Hulme also started racing in Australia, racing in the team of former European compatriot Frank Gardner's JPS Team BMW, which included second in class at the 1984 Bathurst 1000.  Hulme returned to Europe in 1986 racing in the European Touring Car Championship in a Tom Walkinshaw Racing prepared Rover Vitesse. That campaign culminated in a victory in the RAC Tourist Trophy, Hulme's fourth win in the event, 18 years after his third win. After that Hulme raced briefly for Bob Jane's Mercedes-Benz team before linking up with Larry Perkins in 1987, moving with Perkins in 1988 to the newly formed Holden Racing Team. It was with Holden, that Hulme would record his last visit to a podium, when he finished second, in the 1988 South Australia Cup. Hulme would later join Benson & Hedges Racing, another team run by Frank Gardner in 1990. In the meantime, Hulme was one of the founding drivers driver a truck racing craze in New Zealand in the early 1990s running Scania trucks, returning to Europe to race in European Truck Championship.

Using a quote from the above article, answer the following question: What did he do after leaving the GPDA?
He then retired to New Zealand, returning to touring cars to race occasionally in the Benson & Hedges 500 race at Pukekohe Park Raceway