Player character exploration continues complete.
After the leave the game area, I calculate experience, gold xp, and prorate magic item xp.
Sample XP calculations.
The character party meets 4 giant rats.
Two characters defend from, and attack, the rats and kill them.
One character hit 3 of the rats, A, B, and C. The other character hit 2 rats, C and D.
The first character gets all XP for rats A and B, half of the Xp for rat C.
The second character gets all XP for rat D and half for rat C.
The rats had no treasure.
If they had had treasure, it would have been divided up equally amongst the entire character party. Probably no more than a few copper pieces per character.
end of sample.
I would continue this for all combats in that game session.
Any magic items, in my campaign, typically went to who most needed it. Mostly the players would roll percentile dice, if more than one player wanted the item.
Scrolls and any one use items, the XP would all be given to the character who was given the item.
Items that were used for multiple times, got prorated over 10 adventures. A long sword worth 1000 xp would be 100 xp per game session it was used.
I gave out points for each adventure. Excellent 1, Good 2, Fair 3, Poor 4.
When a player character had enough experience to go up a level, I added up those points and divided them by the number of sessions.
So if a player character got all Excellent, then it took 1 game week for them to go up a level. Yes, by the referee guide manual.