Masking imported clips in editor script?

So I'm trying to automate importing a bunch of animations that all have similar format.

So far, I can easily make clips and set their start and end frames. But they also need masks applied to them and I'm not 100% on that yet.

ModelImporterClipAnimation newClip = new ModelImporterClipAnimation();

So I make an array of ModelImporterClipAnimation and assign them to the ModelImporter's .clipAnimations right?

ModelImporterClipAnimation has its own properties, most are easy for me to set up what I want, but the mask is not obvious.

There's a .maskSource property which is of type AvatarMask, and that has a SetTransformActive method. But it only accepts an index to pick which transform. If I want to find the index of a bone according to its name, how would I do that?

 

So the ModelImporter has a .transformPaths property, so I tried looping through that, finding matching strings, and calling SetTransformActive method, but that gets me an InvalidTransformIndex.

Manually going in through the editor, all the animation clips have a "Mask does not match hierarchy" message, which can be fixed by clicking the "Fix Mask" button. Is there an equivalent to that button that I can call from the script?

 

I tried calling SaveAndReimport on the model before setting the masks, but it didn't make the indices get set correctly. Can't think of anything else to try.