What method should I use to author automation if I want to wait for a CloudFormation stack to finish completing in a script?

is a real method, GetStackStatus / get-stack-status is not. http://docs.aws.amazon.com/cli/latest/reference/cloudformation/list-stacks.html

A.
Event subscription using SQS.

B.
Event subscription using SNS.

C.
Poll using ListStacks / list-stacks.

D.
Poll using GetStackStatus / get-stack-status.

Explanation:
Explanation/Reference:
Event driven systems are good for IFTTT logic, but only polling will make a script wait to complete. ListStacks / list-stacks