Taoism is not generally known as a proselytizing religion these days, but was there ever a time when Taoist missionaries were found?
Taoism gained much popularity by the end of the Southern Song period.
When the Mongol Empire started invading, they had the habit of massacring the whole population after a city was sacked. Taoist missionary Qiu Chuji visited Genghis Khan and managed to convince him not to commit any more massacres after battle.
Generally speaking, there were very few Taoist missionaries in Chinese History.
The most famous Taoist missionary would be:
From history and Chinese wiki: In 184 AD plague spread out in China. Thousands of people were cured after drinking ash water from him. He sent 8 major missionaries and around 2/3 of China became his believers at that time. Then they became the major army of the Yellow Turban Rebellion.
Tis rebellion leaded to the end of The Han Dynasty.