Not too fine (which can clog airflow) and not too coarse (which can create an uneven burn)
If, despite your best efforts, you dont succeed in unclogging it, you can visit a shop to ask the sales staff for help

A 2010 CDC study found higher levels of tobacco smoke by-products in people who lived with smokers, especially children, and that, Secondhand exposure to tobacco smoke causes heart disease and lung cancer in nonsmoking adults and sudden infant death syndrome, acute respiratory infections, middle ear disease, exacerbated asthma, respiratory symptoms, and decreased lung function in children. A study in the Journal of Epidemiology and Public Health found that, When compared with never exposed children, children exposed to continuous secondhand smoke scored higher on self-reported aggressive behaviour and teacher-rated antisocial behaviour in fourth gradesimilarly, children exposed to transient levels of secondhand smoke scored higher on aggressive and antisocial behaviour. As you can see from these studies, tobacco smoke is made up of gaseous toxic compounds like acetaldehyde, hydrogen cyanide, and many others

In 2020, New Jersey, New York and Rhode Island enacted bans on the sale of flavored e-cigarettes and California became the second state to prohibit the sale of both flavored e cigarettes and menthol cigarettes.
Okay, so it's not an Irish gin hailing as it does from Germany's Black Forest so just consider this "Schwarzwald" Dry gin a bonus of sorts
The whole idea is for them to feel better at the end than they did at the beginning