Ask HN: What process should I use to find SMB prospects for a B2B SaaS product?

I'm currently trying to build an outbound sales process for our SaaS product. One of the biggest challenges I'm facing is figuring out how to reach out a large number of SMBs. I have previously tried marketing focused approaches but they have been very slow and expensive to do. I'm currently trying to follow the process described by Aaron Ross in the book Predictable revenue. One of the main things I'm trying to figure out is different sources for obtaining highly targeted prospects with contact information.

What are the some of the ways in which you prospect for your B2B products ? What's the best way for me to completely automate the entire process ? Do I hack several products together or go is there some solution out there which already does this ?