Flush Google's public DNS cache
You can use the Flush Cache tool to refresh the Google Public DNS cache for common record types and most domain names. You do not need to prove ownership of the domain to flush it, but you must solve a reCAPTCHA that restricts automated abuse of the service. Flushing any record type for a domain that you have registered or sub-delegated with NS records not only flushes cached responses for the type, it also flushes delegation information about the name servers for that domain. When you have recently changed name servers (by changing registrars or DNS hosting providers) it is critical to do this before flushing subdomains like www, so they are not refreshed from stale data on your old DNS servers.
The only way to flush all subdomains, or all record types for a domain name, is to flush each record type for each domain name you want to flush. If this is not practical, you can always wait for the record TTLs to expire (these are generally limited to six hours even if the actual TTL is longer).