Actually I have used the autoharp to teach both guitar and banjo. Now to be clear, I teach a folk-style of fingerpicking as opposed to the bluegrass or clawhammer style since in adapts to all three of these instruments.

I have adapted several autoharps to my style of playing, and each contains the circle of fifths in the first row, the relative 7ths in the second row and the relative minors in the third row. I convert two of the flats on the twenty-one chord harp (Ab and Eb to Bm and F#m) and explain the picking and listening to the chords, pointing out that all of the notes you need are "here".

The second thing is to find out what key the student is most likely to sing in and that is usually two related keys such as C/G or D/A. However even if its F/Bb or the like I go immediately to the capo to get them in a key they feel comfortable in, as well as chording that is comfortable, such as D/A with modals in Em and Am. This will encourage them to continue even if they stop the lessons and later pick them up, (in which case the autoharp comes back to me).

One of the first things I try and leave with them with is a custom molded set of plastic finger-picks, which I do with a microwave and a mug of hot water. This speeds them up and allows the feeling of the picks "being strange" to quickly disappear, and the autoharp allows the concept of rolls and chord changes to work together. They have a concept they can work on until the next week.

(I am a retired instructional manager of vocational studies from a local Job Corps center and I only have three students, which is all I want since I don't need the money. 60 students... whew!)

The third is the concept of barred chords. I try and teach only three finger chords using the last three fingers, leaving the index to create the barre. I also go straight to "hanger" chords which, given the instrument, and the size of the students hands, may allow a student to make an A chord with a barre across all FOUR of the lower strings with a hanger (little finger) on the fifth fret. Its a much fuller A, and allows the student to go to barred D's etc. Try it 3 frets up for that Bb, 5 frets up for the C and 7 for the D.

I teach the barred forms of an original E, Em, and E7, D and D7, A and A7, B7, Am and only one form of the diminished chords. Don Firth is correct about the bass runs, and I add one more thing. I use tenor guitar chords (the bottom four strings) for the banjo as it allows them to crossover immediately and has the added benefit of allowing key changes with only the switch of the fifth string under a rail spike or a 5th string capo. (Added hint: use a violin Suzuki fine tuner on the other end of the fifth sting to fine-tune the string in a hurry).

Finally I usually meet my students at one of the jams in the area, and I try and insist that they attend as often as possible as it
inspires them to learn at least three new tunes by the next week, even if they don't execute it perfectly. In most of the jams they will only get a chance to pick three tunes, and it helps them learn quicker if they have to start three of them over the course of an evening. (It also teaches the essential jam/session etiquette).

Thanks to others for the above input; new techniques make it more interesting for both the student... and the teacher.