This video covers how to safely scrape google using private proxies.
Private proxies can be very fast and they are reliable because you are paying for them. That said using only a couple of connections on private proxies can be as fast as 10-20 times that many connections with public proxies.
Another advantage is that you don’t have to constantly obtain lists, you simply keep using your private proxies because you don’t get them blocked. This method also generally works with shared proxies as well.