Basically, I'd rig it like I would any multi-purpose 360 turning rig. How complex you make the rig depends on the design of the character and how accurately/precisely you wish to interpret the dance moves.
One method is to rig like a Character Wizard setup, that is, create a simple single-direction rig for each facing angle and place them inside a switch layer. Do the body and head separately so they can turn independently of each other. You can switch between these rigs using the Switch Selection window (easiest) or any number of other methods including ctrl-alt-r mouse clicking in the workspace (calls up an on-screen list), using a smart bone dial, or r-clicking on the layer directly (for a list). (I've used all of these methods in production and these days I favor the Switch Selection window.) The downside with this setup is that, while it may be easier to setup, it's also harder to animate because you'll need to match pose whenever you switch views, which can get tedious. (Personally, I avoid this approach and only do this when I'm required to rig many characters in a very short time quickly.)
A better but more time-consuming approach (for rigging) is to use Smart Bone Actions to modify your drawings as they turn. Some character designs allow you to do this smoothly, others (probably most) will requires at least some switching of drawings. Like in the above, you want to separate the head and body so they can rotate independently. I also like to make the arms and legs separate to so they can rotate independently. This kind of rig takes more time to set up but it can be much easier and faster to animate, so you make up that time and then some if you have a lot of scenes to animate.
A good 'simple' example of this approach is the rig I made for the Netflix Puss-in-Boots series seen here:
Puss-in-Boots Interactive Demo Reel. The beginning of the video demonstrates how all the parts turn. No real dancing is shown but if you scrub to 0:48 you can see a neat 'Flamenco-style' 360 degree turn.
Whichever way you decide to go, download some good dancing reference footage to work from. YouTube is full of them, including instructional ones that tell you exactly what's going on from step to step. I was recently asked to make a character dance for project at work, and I referenced parts of dance clips I found on YouTube to create my own choreography. In this case, I was animating a 3D character in Maya but the same applies to animating 2D characters in Moho. The easiest way to do this is to load the reference video in a video editor, mark the beats and key poses, add notes to the frames, and then render out a jpeg image sequence and separate uncompressed AIF or WAV audio track. These files can be imported to Moho and used as frame accurate reference.
When animating a dance, I suggest doing that in multiple passes. In other words, animate only the key poses first and set the keys to step. These should fall on or near the beats. Review this and adjust the timing as needed. Once you get this looking good, go back to the beginning, change interpolation and add the in-between keyframes where necessary. Once you get that pass done, go back again and adjust your poses and timing to get the strongest and most energetic performance you can from the rig. Follow these steps and the dance animation will be completed in no time.
Actually, this workflow can apply for almost any situation, not just dancing, but I find it most helpful for animations that need to be tightly synced to the audio.
Hope this helps.
