Here some simple tips that have worked for others who searched for policy:

Just want longer reports, no blog posts? Add filetype:pdf to your search. This typically will return reports. Toggle for "Date" on the top right, and you will get the most recent reports. 

Want to exclude Brookings? Add to your search. Similar exclusion works for other institutions or individuals.

Entirely new to a policy field? Run a broad search, and find two or three key terms that allow you to do a more focused second search. 

Let us know whether you find any particular challenges.