how can I set up my netcfg profiles to use the google DNS servers? I've tried
IP = 'dhcp' DNS = '18.104.22.168'
but that didn't cut it.
You should be able to put the custom DNS addresses into your DHCP server's configuration, so your clients get told to use them instead of the defaults.
If your DHCP server is a router and it doesn't give you the ability to change the DNS addresses, you can always run your own DHCP server. There are other reasons to do that besides custom DNS server IPs. For example, dnsmasq will act as a LAN DNS cache, too, and integrates the DHCP and DNS so you get nice features like the ability to