Arranging a song from a 6-string guitar to a 3-string cigar box is an exercise in discovering the essential notes and chords. To do it right, you have to find the truest essence of the song (the main riffs, melody, etc) and convert it to a very simplified string setup.
France's Jerome Graille is a guitar teacher who discovered the cigar box guitar and has been making fantastic videos on his Youtube channel for many years. His latest video features a stripped down version of Born to Be Wild, performed on a 3-string cigar box guitar with both slide and fretted notes. His version manages to keep the entire heavy metal thunder essence of the song. Sure, he's not playing ALL the notes originally performed on guitars, bass and Hammond B3 organ, but you still know exactly what he's playing and your mind fills in the gaps.
To me, this is a great example of the pick-and-choose nature of arranging on cigar box guitar.
Learn more by checking out his new website, CigarBoxGuitarMusic.com (English speaking folks might need to run the site on a browser that features a translator.)