Some people like receiving oral sex from someone with a mustache, as the hairs can provide additional stimulation. Others may find a mustache too abrasive, making oral sex uncomfortable.
The fact that the odors of oral sex can also linger on a mustache, serving as a reminder of the sex act after it has occurred, is appealing for some people.
In terms of how to give a mustache ride, it's important to consider the comfort of both partners. The partner on top may need something to support themselves in order control the intensity of the stimulation and ensure their partner can breathe. Queening chairs exist for this purpose, but a couple of firm couch cushions can also help elevate the receiving partner. The partner on the bottom should ensure good communication occurs between both partners and that there is a nonverbal signal to stop play.