Ask HN: How to find a marketing genius?

We are launching in an hardware startup in the cleaning field. We are both very techy. We had no previous experiences on the business side, but apparently we are not so bad there. However, we know that we will soon need a guy to bring a more detailed analysis of the market, implement processes, and negotiate contracts. As we have good backgrounds in tech, it is easy for us to interview tech profiles. As we are still learning in business, we don't know how to be sure this is the good guy, and what to expect from him/her. Would you have some advices for interviewing people in marketing and find which one would be our associate?