B1F surfing only has slowpoke as an encounter. This would be better to not have phases.
On B2F surfing, you could lead with a fainted level 10 Pokemon and use repels to force slowpoke as the only encounter.
https://m.bulbapedia.bulbagarden.net/wiki/Slowpoke_Well
If possible, hunting in multiple games at once help a lot—I hunt in two to four games at a time. But that’s a lot of money and may not be an option for you.
Try to hunt passively, like while cooking or watching tv, or studying. Helps with burnout.
I used to take my ds to school and do it in lectures. I don’t recommend, because some teachers get aggressive about that, but it helps get those encounters in.
Some people livestream or record their hunts to preserve sanity. Become a famous pokehunter and livestream your hunts, lol. Or on the contrary, find a poketuber doing shiny hunts live, and watch them while doing your hunt. One guy got to 70k encounters with no shiny; it made me feel better about my own luck.
The Cute Charm Glitch might be something worthwhile to look into, as that raises the odds tremendously, but that’s requires a new save file.