Maximizing Outreach: Finding Contacts for 3,600 Companies

I need someone's help to maximize the number of people per company. I'm getting 3,600 companies from ocean into clay, then using find people at these companies and filtering Founders (1 per company). There will be 3,600. Then find emails using email waterfall with leadmagic&prospeo. However I'll still have a lot of founders without an email address. So is there a good way I could lookup for the companies without a contact and find Co-founder/C-level person? The goal is to reach out the to as many companies as possible out of 3,600 companies on the list with conditions - if founder email not found, find co-founder/c-level exec, if cofounder/c-level exec email not found, find sales director, etc. Thanks! P.S. I'm not looking to outsource this - I need a simple direction on how to do it.