My go to defenses to get rid of the larvae are BTi, nematodes, and OG Biowar. Of those, the BTi is most convenient. I usually use Gnatrol WDG because it’s a powder and I can mix it stronger than mosquito bits. Nematodes are awesome, but it’s hard to get them alive here, at least not reliably. OG Biowar works okay, but it’s not as good as claimed and is expensive for what you get.
Gnat Nix! on the surface and sticky traps on pot edges keep the flyers at bay.
I can usually completely eliminate an infestation of I do those things immediately.
YMMV. Good luck, I hate those bastards! I hope they stay away this time!