How can Scrapebox scrape blogsearch.google.com?

For scraping blogsearch.google.com you need to add this to custom googles (drop down arrow next to google in the select search engines in lower left quadrant of main GUI)

google.com+&tbm=blg&

Then make sure its checked off when you hit that same drop down arrow. The reason they haven't specifically included it is that Google includes a lot of non blogs in there. Like scrapebox.com for instances is there, along with lots of forums, and lots of other stuff, so a custom footprint that searches for blogs is going to provide more accurate results compared to the google blog search.