TL;DR: I'm looking for a technique for handing out XP during sessions that is both rewarding for the players and easy to handle as the GM. Doesn't have to be RAW; personal experience is welcome.
I GM a roleplay heavy homebrewed 5e campaign for two players. We've been fudging the rules left and right to make it more fun for us as a group, but I've hit a wall when it comes to XP.
My players really like the idea of getting XP on a per-encounter basis (whether this is combat-only or (more likely) from roleplay as well) because they like the constant "praise" and the sense of accomplishment. They also seem to take a sort of glee out of writing down the incredibly stupid reasons they got XP so they can go back and laugh about encounters later. If it was something I was fluent in I would love to similarly give them laughably small amounts of XP for things I thought were in-character, funny, or creative (kind of like inspiration, but as XP).
The problem is that the mechanics of the system they want are overwhelming for me. I tend to make things up on the fly (both roleplay and combat encounters) and therefore haven't planned ahead and have no idea how much XP any one section of play should be worth. I also just tend to forget. A lot. Like literally every single time they probably should get XP it's so far from my mind that I often don't remember XP is a thing until half a week after the session when I get a d'oh moment. I'm new to GMing and handing out XP is not a simple thing for me; calculating the correct amounts takes me time to not mess up.
I tried remembering to keep a rough tally during play and hand them a "session" XP tally at the end of each game, but I tend to either forget to tally bits, or be so wiped by all the fun we had that I don't have it in me to do the math post-session.
My preferred solution would be to just have them level up when it makes sense for our narrative, like at the end of each story arc, or after a certain amount of time had passed in-game. This doesn't give them the feedback they're looking for however, which I appreciate and am therefore looking for ways to resolve.
Does anyone have similar experience with XP in their games? How did you handle parceling it out?