Another cool trick is using tailscale to ensure your portable devices always can access your Pihole(s) from anywhere and then setting those server's tailscale addresses as your DNS servers in tailscale.
This way you can always use your DNS from anywhere, even on cell data or on public networks
I keep a third instance of Pihole running on a VPS and use it as the first DNS server in tailscale so it will resolve a bit faster than my local DNS servers when I'm away from home