When people say that physically unattractive or otherwise undesirable men just need to learn to flirt with women in order to show off their confidence and build attraction, it sometimes seems to be overlooked that flirting itself is a two-way street, and usually facilitates attraction which is already present to some degree. It is not a one-way process, or at least it can't persist very long if it's only one-way. Attempting to flirt with someone who isn't interested and is not at all reciprocating is akin to attempting to play tennis with someone who declines to return your serve, or trying to perform a standup comedy routine in which the audience just sits there stone-faced and unlaughing.

Yes, men (and women, of course) should work on flirting and learn to read signals if and when they present themselves, but attempting to flirt with an unwilling partner is just not going to go anywhere. To a certain degree, telling undesirable men that they need to get better at flirting in order to attract women skirts the line of simply telling them that they need to be attractive in order to attract women.