Best ways to replace count_scalar() in Prometheus?

With the recent release of Prometheus 2.0, they removed the count_scalar function and unfortunately there were a lot of dashboards that relied on it. I have been trying to replace it with absent() which mostly works but not in all cases.

I am far from an expert in PromQL and mostly muddle my way through, so is there anyone that has a far better grasp of this to help explain how it works better and what are some good ways to replace it's usage? Thank you!

-Adam