Log into your main character, go to Rata Sum, enter the box, and start from Zone 1.
Zone 1 : Nothing special. Just rush past all enemies, don't waste time opening chests or killing anything. Just get to the end. At the end, run around the cage in circles while you auto attack. Loot the chest, port to Zone 2.
Zone 2 : Run to the Shortcut Worm, you can find other posts in /r/guildwars2 showing you where he is. It'll take you right to the end. Do the same as before, strafing/autoing the cage, loot, and port to Zone 3.
Zone 3 : Some people think Zone 3 is inefficient, I disagree. Why? Because chests have a chance of dropping skins. And the chance isn't THAT low. I've had 4 guildies loot skins. They sell for upwards of 10G right now, and will likely increase once the event ends. I've looted one skin.
Zone 3 is similar to 1 and 2, in that you can just rush along to the end. Feel free to jump through the poisonous water, if you spam jump you can avoid damage. Just rush.
The frog seems hard at first, but he's really not that bad. Jump up to his lilly pad and immediately start whacking his necklace. Once a piece falls off, pick it up. While you're doing this, you want to watch for his attacks, he has 4.
Attack 1/2 : Lifts left/right leg and stomps it down, creating one small wave. You can just dodge to avoid. If you stand near his necklace at all times, you can just dodge backwards for all of the dodges I mention.
Attack 3 : He squats down and charges up. You need to GTFO. Jump backwards onto some lillipads/one of the rocks. 2 big waves will come, you can dodge one, but one will hit you if you stay too close.
Attack 4 : He looks left and right, then opens his mouth. When his mouth is open, you throw the jewel in. Then he'll fall forward and you can damage him. If you don't have a jewel, he'll stick his tongue out towards the right, and sweep it across. If you dodge front/back while standing near his jewel, this attack is also completely avoidable.
Once you get used to the kill, the fight only takes ~2 minutes, and I'll explain why it's worth it.
Repeat : Next thing to do, is log off, pick a new character, and repeat these steps.
Repeating with alts : If you run out of characters to do this with, you want to make a new character, an Asura, finish the intro, do the box, delete him, and repeat. THIS is when doing Zone 3 starts to become worth it. Faster repetition is just more wasted time doing the intro/character making. You're better of taking some time to do Zone 3, to increase your chances of looting a skin, and decrease your wasted time.
Argument for why Zone 3 is worth it :
From character creation to end of Zone 1 isn't 6-7 minutes, it's 9 minutes. Unless there's something I'm missing and you're able to skip that little introduction cinematic that plays for Zone 1.
/age read 4 minutes at the time I was standing infront of SAB after a new character.
/age read 6 minutes after the cinematic for Zone 1 played.
/age read 9 minutes as I was waiting to warp to Zone 2.
/age read 13 minutes as I was waiting to warp to Zone 3.
/age read 18 minutes when Frog boss died.
I'll give warping back/banking/deleting character a time of 1 minute. It'll be even across both examples.
If I stopped at Zone 2, I would be completely finished my run in 14 minutes. That's 12 bubbles in 14 minutes, or 0.857 Bubbles/minute.
If I stopped at Zone 3, I would be completely finished my run in 19 minutes. That's 18 Bubbles in 19 minutes, or 0.95 bubbles/minute.
All /ages were checked while moving towards a destination, and I NEVER stopped. Zone 1 and Zone 2 were perfect runs, the only part I actually got slightly caught up on was Zone 3, and it was for ~10 seconds.