Both phones enter scores into the same card. Everything still works with no signal and catches up when it returns.
Send the share link to your other scorer — it carries the database and room code, so they just open it and start scoring.
One-time setup — where the database URL comes from
Go to console.firebase.google.com and sign in with any Google account.
Create a project — name it anything. Turn Google Analytics off when asked.
In the left menu: Databases & Storage → Realtime Database → Create database. Not Firestore — it must be Realtime Database.
Location: pick Belgium (europe-west1). Rules: choose Start in test mode, then Enable.
The database screen now shows a URL like https://your-project-default-rtdb.europe-west1.firebasedatabase.app/ just above the data panel. Copy it and paste it in the box above.
Tap Test. If it says Connection OK you are done. Then tap Share link and send that to your other scorer.
Test mode leaves the database open to anyone holding the link, and expires after 30 days. For golf scores that is fine — just create it in the week of the trip. To tighten it, set the database rules to {"golf": {".read": true, ".write": true}}.
Who can do what
Everyone shares one link. These two decide what each person can do with it.
Setup password — organiser
Scoring PIN — the card keeper in each group
Players & handicaps
Tap D1 / D2 to set who plays which day.
Handicap allowance
Playing handicap = handicap × allowance, rounded to nearest whole shot.
Course card
Pick a saved course for each day, or edit the par and stroke index by hand and save it as a new one.
My courses
Saved cards you can pick for either day. Set a day's card up the way you want it, then "Save to my courses" to keep it for next time.
Data
Scores save automatically on this device. Take a backup before the round if you want a safety net.