In May, a high-profile trial opened against Dongguan's "hotel king" Liang Yaohui, 48, who was once listed among China's 500 richest people and was a deputy to the National People's Congress, China's Parliament.
Forty-seven people - all stakeholders or employees at the five-star Dongguan Crown Prince Hotel - were charged with organising or facilitating prostitution, which is illegal in China.
The hotel generated close to 50 million yuan in illicit income in 2013, according to reports. Liang, the hotel's chairman, has denied the charges, as did three others. The rest pleaded guilty. Liang could face the death penalty if found guilty. A recent visit by The Straits Times found the hotel open for business, but its seven-storey sauna centre was closed, its glass entrance blocked by large potted plants.
More than a year after the crackdown, the effects are still being felt in Dongguan. Employees at nightclubs and massage parlours say the number of customers has plunged by more than half and that the authorities have not let up on checks.
"Why don't you call the police and check with them?" one massage parlour receptionist replies tersely, when asked if sexual services were still offered in Dongguan. At the Tianerhu red-light district in Changping, bright neon signs with the Chinese characters for "massage" dot the streets, but on a Saturday night there were few people to be seen.
A massage parlour that once employed up to 300 girls has had to let two-thirds go, says an employee.
At one nightclub, three customers were drinking and singing karaoke. "We no longer have any girls on our payroll, so the customers stopped coming," the manager says, adding that businesses have remained wary of the police.
At the height of its boom, it was estimated that Dong guan's sex industry generated 50 billion yuan in business, or about one-tenth of the city's revenue.
The crackdown has hit the city hard, even in sectors that are not directly related to prostitution. Mr Yu Licheng, for instance, had opened a restaurant three months before the crackdown, ploughing 500,000 yuan into the business .
Business was good initially and he could make about 50,000 yuan a month. Once the crackdown started, his earnings "practically dropped to zero".
"The girls go to salons to get their hair and nails done. They buy new clothes. They rent rooms in apartments nearby. Everyone goes out for supper at night. Businessmen throw money everywhere. So when the authorities cracked down, many people were affected," says Mr Yu, 32.
That is not to say that prostitution has been completely eradicated in Dongguan. Mr Ma, the factory manager, says it is still possible to arrange for sexual services.
"They're not allowed to openly offer services as in the past, but we have maintained contact with relevant people and we can make calls."
Sex workers have also turned to social networks like WeChat, where a search of "People Nearby" throws up women with suggestive pictures and contact details.
During a visit to a nightclub in the town of Humen in Dongguan on a Sunday night, a manager sidles up with a proposition.
"If you pay 550 yuan, you can get a drink and she'll accompany you," he says, pointing to one girl. "After that, you can do whatever you want, you negotiate."
But the scale is clearly not what it used to be, which may displease those whose business has been affected. But to locals like shop assistant Zhou Xiaoli, 27, the crackdown is heaven sent.
"In the past, whenever I tell people I'm from Dongguan, they'd give a knowing look and smile, and say, 'Yes, lovely place'," she says.
"I don't want my hometown to have this kind of reputation. Many of us make an honest living."
As with China's ongoing anti-corruption campaign, nobody knows for sure when - or even if - the crackdown in Dongguan will end. Locals see no immediate let-up.
Back at the music bar in Changping, it is 2am and a middle-aged customer beckons Xiaofeng over.
He puts his arms around her and asks for a photo. She giggles as the picture is taken, then takes a tip from him as he gets ready to leave.
"I don't make even half of what I used to," she says. "Many of my friends have left Dongguan for places like Huizhou and Shanghai. I think I'll join them soon."