What are some strategies or techniques to help sales reps sell to CFOs?

A clear focus on the available ROI always seems to produce much improved outcomes, particularly when their's clear evidence that the math sitting behind it is accurate and not a "stretch."

You must have a basic understanding of the firm's Financial Statements - Balance Sheet, Cash Flow, Income Statement - and what they mean about the company you're attempting to sell into. You can get a lot of that from the Edgar database at https://www.sec.gov/edgar/searchedgar. You can also look up 10K, 10Q, and 8K information.