I have setup several PiHoles for others. I used a Pi ZeroW, got the software installed and tested at home (I use the 192.168.0.x range), then cloned the card for each subsequent install. I didn't go crazy with blacklists, I used the defaults and the ticked lists from wally3k ([https://firebog.net]).
I keep a record of the MAC ID, password and installed IP for each Pi I set up, helps to troubleshoot later.
To get the Zero W to talk to their wireless network, I put a "wpa_supplicant.conf" file in the root directory of the Pi I set up for each person. This file has the details of their wireless network so the Pi can connect. Contents are as follows:
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
network={
ssid="putSSIDhere"
psk="putpasswordhere"
key_mgmt=WPA-PSK
}
Then, once the Pi is on their network, log in to Pi via SSH or VNC or whatever you use, and run pihole -r to get the Pi IP address where you want, and then make this a reservation on the modem. Then change the modem DNS settings to the Pi (sometimes you have to list the Pi IP twice, as some routers insist on two DNS addresses).
I also changed the Pi password to something of their choosing.
Lastly, reboot any IOT devices and disconnect/reconnect other devices from the network, so they will get the new DNS address. You may have to flush DNS caches, depending on the device.
I usually monitor the Pi for just bit by tailing the PiHole log and ensuring that the devices are talking to it.
I haven't set up VPN for remote support. My sister and brother live 1500 miles away, and I had them call me on Skype when the devices arrived in the mail. We screen shared and I walked them through the setup steps with no problems.
In my opinion, having a local PiHole is going to be much faster than serving one remotely in the cloud, and at an installed cost of less than $30 it's not very expensive.