Higher Engagement Than Most
By only having 2 questions, you will get a higher response rate. Pick a score 1 out of 10, optionally leave comment and you are done.
Filtering Who Gets It
Only show the survey to customers whose account is greater than (x) days so your new clients have time to learn the system before reviewing it.
Hide it for a few days when closed
When a customer closes the survey, you can prompt them a few days later, or a few weeks later.