For B2B I manually research ideal customers and manually reach out via cold email. I'd send a few hundred. If you don't get any buys from 200 emails sent to your target market you probably don't have a business.
Once I validate and start getting traction only then I start automating cold email, ads etc. Do not validate with automated cold email agency. You can't automate something well what aren't doing with success already manually. Nothing beats manually researching your prospects and writing up personalized email - only when you understand this process and you know how, where and when to find your ICP and what to look for and what to tell them only then you can automate this process.
You want to automate processes that work already. Not the other way around.
Built a few businesses with this approach and still works today in 2025.