I imagine that when seeing a Megatar for the first time a lot of people say something like:
 “No way I can play that thing, are you nuts?  I have a hard enough time with 6 (or 4) strings.”
In response I say:
If you have piano training, it helps a lot.   If you can play bass, your good to go.  If you can play guitar, great.  If you dabble on all of them, even better.
If anybody ever learned to play guitar or keyboard, then you can learn to play the Megatar.
Did you know that on a piano the left and right hands have to learn different fingering patterns for each scale/key and that each key signature demands a different pattern of black and white keys?  On the Megatar the patterns for major scale, minor scales, blues scales, chord forms, etc. are the same regardless of what key and where on the fretboard you are.
There are a lot of notes (300 to be exact), but you don’t need to play them all at the same time. 
It might look intimidating, but when tuned in straight 4ths the geometry and patterns of the fretboard are easier to comprehend than standard guitar tuning.
If you think you could figure out how to play bass, this is just more of the same, but the actual playing technique is easier than bass or guitar because both hands are using the same technique.  Such that one hand does not need to learn a bunch of different stuff like, picking, or finger patterns, slapping, strumming, etc.  Rather both hands use the same technique.
Organ players regularly play with each hand on it’s own set of keys while also using their feet to play bass patterns.  Playing a Megatar is easier than that.
Accordion players play with both hands, and work the bellows at the same time.
In fact there are a lot of instruments that are much more difficult to master than the Megatar, and thousands of touch-style players around the world have proven that it can be done.
Standard bass instructional materials apply to the 4ths tuned Megatar, especially those geared toward 6-string bass and/or fretboard tapping technique. 
Any bass player who knows their way around a 6-string bass will be able to make sense of a Megatar. And what the left hand already knows flows quickly over to the right hand.
Every instrument ships with a set of 4 method books, a fretboard map and a music theory chart to get you started.
Tappistry.org is an online forum dedicated to two-handed tapping on any stringed
instrument and is a great resource for asking questions, connecting with other players and learning to play the Megatar.
If you choose a Chapman Stick style tuning there is a wealth of great instructional material and resources out there and an active forum.  Just don’t let them know your playing a Megatar or you might get hurt.