Approach market research/customer discovery the way you would most early startup decisions; keep it small, cheap and be ready to iterate. Instead of focusing on a list of hundreds of companies to contact, start with your own assumed customer profile. Call a few of those profile customers and listen to what they have to say.
After you've established what that initial group has to say, iterate your research accordingly. Continue the process until you can predict what the person on the other line is going to say because you've heard the same sentiment so many times from customers.
I've done a lot of this work, so fee free to ask me any follow up questions.