Purchase a cup of black greasepaint.
Smear the greasepaint above your upper lip in a thick, rectangular strip using your finger or a rag. Extend it slightly beyond the width of your lips.
Examine your mustache in the mirror, and make any touch-ups you feel are necessary. using a clean portion of the rag or a tissue.
Visit your local toy store or joke shop, or go online, to purchase a fake mustache. Look for a wide, thick mustache or a "Groucho Marx funny mask," which includes glasses, a nose, bushy eyebrows and a mustache.
Peel the paper backing off the mustache. Place the mustache above your upper lip. If you purchased a pair of funny nose glasses, put them on.
Check in a mirror that your mustache or mask is on properly. Trim the mustache if it appears to be too long or is bothering your lips.
Let your mustache grow uninhibited, much like Groucho did later in life.
Shave your neck, chin and cheeks periodically to ensure that the only hair left is on your upper lip.
Check your appearance in the mirror and trim your mustache as needed so that it extends wider than your lips but doesn't hang over or hide them.