Bold section is the hardest timing. You should press

immediately after the last FREE BEES!
Bee: HELL NO WE WON'T WORK
Chorus and YOU: HELL NO WE WON'T WORK

Bee: BOGAN IS A BIG FAT JERK
Chorus and YOU: BOGAN IS A BIG FAT JERK

Bee: HELL NO WE WON'T WORK
Chorus and YOU: HELL NO WE WON'T WORK

Bee: BOGAN IS A BIG FAT JERK
Chorus and YOU: BOGAN IS A BIG FAT JERK

-----------------------------------------
Bee: ARE WE BEES, OR ARE WE FLIES?
Chorus and YOU: ARE WE BEES, OR ARE WE FLIES

Bee: NO MORE LIES! NO MORE LIES!
Chorus and YOU:NO MORE LIES! NO MORE LIES!

Bee: ARE WE BEES, OR ARE WE FLIES?
Chorus and YOU: ARE WE BEES, OR ARE WE FLIES

Bee: NO MORE LIES! NO MORE LIES!
Chorus and YOU:NO MORE LIES! NO MORE LIES!

----------------------------------------
Bee: SEA BEES!
Chorus and YOU: SEA BEES!

Bee: FREE BEES!
Chorus and YOU: FREE BEES!

Bee: SEA BEES!
Chorus and YOU: SEA BEES!

Bee: FREE BEES!
Chorus and YOU: FREE BEES!
Everyone including YOU: WE'RE STRONG
Everyone including YOU: WE FIGHT

Bee: We're Killer Bees Tonight
Everyone including YOU: ALRIGHT
Everyone including YOU: WE'RE STRONG
Everyone including YOU: WE FIGHT

Bee: We're Killer Bees Tonight
Everyone including YOU: ALRIGHT

---------------------------------------
Bee: MANNY, MANNY, CAVAELRA
You: ME, ME, ME-ME-ME

Bee: GOT NO SKIN, GOT NO HAIR-A
You: GOT NO SKIN, GOT NO HAIR-A

Bee: MANNY, MANNY, CAVAELRA
You: ME, ME, ME-ME-ME

Bee: GOT NO SKIN, GOT NO HAIR-A
You: GOT NO SKIN, GOT NO HAIR-A

This helped me greatly and was a comment in your solution (Thumbs up on solution too btw).
Walk towards the little green light on the left so that Glottis will start talking to you. After a while, a guy walks from the left to the right. When the little dude (called Chepito) wearing the lamp is close to you, interact with him and go through the conversation options. If you miss him, wait for a bit and he will eventually turn up again. There's an annoying conversation option where Manny asks if you can tag along with him. I'm not sure if this option is needed for the achievement, but as I accidentally selected it, and got the achievement a little bit later, I can't go back to check. So just do the walk and grab a drink in the meantime. Or sing along, whatever floats your boat (pun intended). After finishing the conversation, you will unlock:
I confirm they aren't all needed. Rewrite it like this to save everyone time:
Walk towards the little green light on the left so that Glottis will start talking to you. After a while, a guy walks from the left to the right. When the little dude (called Chepito) wearing the lamp is close to you, interact with him and go through the conversation options. If you miss him, wait for a bit and he will eventually turn up again. Don't choose any option that says "Go with you". Exhaust the second to last conversation options (the one above saying goodbye to him) and stop talking to him after that to unlock:
All done now. Great WT man tyvm