How are you using FB post boosts to grow blog engagement for new SaaS business?

I actually have good experience with "boosting" posts. You just can't do it with every post.

1. Your Facebook post must have a hook. Something like a spoiler, but which leaves questions open. Something that gives a reason to click.
2. Your blog post must be really, really, really, good. No, not like that, I mean really, really, really good (btw, if it's that good, you can market it everywhere, not just FB. If it sucks, you shouldn't market it anywhere).
3. If you want to sell your product, you better make sure that your product is, well, really, really, really good... But don't expect it to happen for the first time when you advertise your blog. You'll have to do it repeatedly and try to hit the same people as before, then slowly the sales will pour in.

Don’t boost posts, it’s a waste of money. If you want to run FB Ads use the ads manager and choose the conversion objective.