I'm doing an animation that involves interpolating between two Paths on a
Shape Layer. I'm having some problems getting it to animate the way I want.

In the old days when doing this kind of thing I used Solids with Masks and
when I had a problem I used the Smart Mask Interpolation panel to correct
and smooth out the interpolation. It used to work fine. Now, with CS3, I use
Shape Layers, which has always seemed a neater and faster to achieve the
same results, but this is the first time I've had an issue with
Interpolation.

Am I being dumb, I can't see a way to do for two paths on Shape Layers, what
the Smart Mask Interpolation does for two Mask Paths. The Smart Mask
Interpolation doesn't want to work with Shapes (the clue is in the name I
guess). I did check the manual but couldn't see an answer.

My solution was to add a Mask on the Shape Layer, copy the Keyframes from
the Shape Path to the Mask Path, link the Shape Path to the Mask Path via an
expression using the Pickwhip [ mask("Mask 1").maskPath ], then run the
Smart Mask Interpolation on the two Paths on the Mask Layer which gave me
the animation I wanted.

But is this really the only way of smoothing out Interpolation problems
between two Paths on a Shape Layer?