Here are some bonus tips related to the Gap option:
Sometimes I'll split a drawing between two layers, for example, I'll draw a single arm and split the curves through the elbow so the arm has an upper shape and a lower shape. Then I'll duplicate this layer and knock out one shape in each layer so I see a complete arm when both layers are visible. This is useful when I'm using Animated Layer Order or animated layer visibility to make it appear the arm is wrapping around the torso.
One problem with this setup is that when I render the arm, I'll see a thin gap where the arm edges should perfectly align. This is caused by Moho's Anti-aliasing. You can see this by disabling AA and then rendering; the gap should now be gone.
How, if this art is going to be used as a mask, just disable AA for both layers and the gap will disappear and everything should be fine.
However, if this art is for the color render, you might think the Gap option will fix this problem. Unfortunately, the Gap option only works between adjacent shapes that exist in the same layer, not two separate layers.
Fortunately, fixing this problem is pretty easy: just add a point to the dividing line in one of the layers and then drag that point a few pixels to make the line overlap the line in the other layer. Because the layers are now overlapping, we've eliminated the possibility for the gap.
If you're compositing in After Effects, another option is to render with no AA at all and then use the free OLM Smoother plugin to add the AA in post. This is a best approach if you intend to use other OLM plugins since these tools work best on hard non-anti-aliased edges. You can find the OLM plugins here:
OLM Tools