Thanks for all the good suggestions!

A neighbor (who used to have a business stamping cement) suggested we use a paintbrush to feather our patches. The vermiculite particles clung to the bristles, and now we have a bunch of ruts and ridges. I'm going to have to spend quite a bit of time smoothing them out now, before we can drop the liner. (Although he was trying to be helpful, I don't think I'm gonna take my neighbor's suggestions without first bouncing them off of you.)

When sweeping, we have noticed some more places where the original surface flakes up, thus creating the need for more patching. Frustrating!

-Andy