As Martin has stated, what you have is good to go. I will just add a few pointers that I hope will add clarity which should help you and others better delineate the workflow, for future work.
(1) Open Mocha AE CC.
(2) Create an X-spline or a bezier layer that extends a little beyond the outer edges of the sign (since these edges might help mocha in achieving good tracking).
This is the Tracking Spline(s). Your workflow begins with drawing one or more Tracking Splines.
It’s a good idea to pay attention to which features you want tracked + the percentage of pixels, within the Tracking Splines, which will be used by mocha to track. The percentage of pixels setting is akin to the tracking resolution – a higher value equals tighter tracking data which may or may not be redundant; depending on the complexity of the tracking requirements and off course, a higher value means longer computational times, although the latest mocha products are finely tuned for GPU acceleration.
(3) Track everything and adjust (create keyframes) the X-spline or bezier after tracking if needed.
(4) Create a new X-spline or a bezier layer, but make sure it sits right on the outer edge of the sign this time.
This is the roto spline and is only required if your insert object/region cannot be perfectly shaped by four corner points – it four corners are appropriate then all you need to do is to apply the Surface Area and export out Corner Pin tracking data. For other shape types, an articulated matte is required.
(5) Link the new X-spline or bezier to the original (motion-tracked) X-spline or a bezier; this will make the new X-spline or bezier follow the motion of the original.
(6) Go through the frames and adjust the new X-spline or bezier layer until it fits really good.
Adjustments to refine tracking accuracy can be in the form of additional/repeated tracking with new/old keyframes OR via the Adjust Track Module.
(7) Export to AE and apply the mask from there (you’ll end up with a sign on a transparent background).
Is this a good workflow?
You’ll now off course have to use the shape data/layer as a matte for your insert object. Critical to all of this is the requirement to also export tracking data; Translations and or Corner Pin data for your insert layer.
HTH
Roland Kahlenberg