Sign up for Apollo.io and research people by job role, company etc. whatever you need. Set up a sequence with daily emails and try to add as many people as you can (100+ for sure) to the sequence. Compensation would make this easy. Without compensation, your could try to position it as exclusive - “invitation to expert panel” or tell them the research can help solve the #1 pain point they have in their role (research online what that might be). Use chat GPT for high performing subjects lines and try many variants. Keep emails very short and provide a link to set up the call (for example Calendly) right away.

Apollo.io mass cold email outreach based on job title (you find them in the tool). Offer an incentive for their time and drop a calendly link to book a slot directly from the email.