How the strategy works:
This tactic was discovered by PEEFsmash and was documented first in Pokemon GO- Gamepress website. They said that in able for this strategy to work, you’ll need to utilize a 10 CP Level 1.5 Diglett with the with the appropriate IVs and moveset, to defeat a 20CP Horsea, Krabby, or Poliwag with Bubble and appropriate IVs without taking any damage. They call this the Bubblestrat and this tactic will reward 1000 Gym Prestige and 100 trainer XP per Bubble-Pokemon defeated, and takes only seconds while requiring no revives or potions even if you mess it up!
This works by exploiting the long startup-animation of Bubble, by killing the Bubble-User before they can get off a single attack. (Diglett will often go invisible after the first fight. This is itself not part of the tactic, but is just a regular occurrence any time you defeat a Defending Pokemon just before it would do fatal damage to you).
The DO-IT-YOURSELF METHOD:
First, you need a Diglett. This Diglett has to be caught at Level 1. All Level 1 Digletts will be caught at 10CP. At this point, you will need to power it up once, bringing it to what we call “Level 1.5.” The Level 1.5 Diglett will need to remain 10CP. If he is 11CP, his IVs are too high to use the tactic (and you won’t know this until you actually power him up once). Now, once you’ve got your 10CP Level 1.5 Diglett, he still isn’t guaranteed to be useable. The minimum Attack IVs required for the Diglett to do 4 damage per Scratch or 5 damage per Mud Shot (if you’re lucky enough to have a level 1 Mud Shot Diglett lying around) will be determined by the species and defense IVs of your Bubble-using gym defender…
So, let’s describe our potential Bubble-users:
There are exactly 3 species capable of serving the punching-bag role. They are:
These are relatively weak, unevolved Pokemon that can learn Bubble. They will stand in, start to attack, and do us proud by dying before they can hit you with the incredibly slow Bubble. The order I have listed them is the order of likelihood of having the correct IVs.
Horsea, for instance, are quite likely to have the appropriate IVs as the tolerance required allows for many IV Horsea to work. Because your Diglett might have any attack IV, it is not possible for me to tell you which Horsea will work exactly, but it needs to be at least 20CP when powered up once to Level 1.5, and its defense IV must be no more than 7 higher than Diglett’s Attack IV.
For Krabby, the window of workable IVs is smaller. Again in addition to needing to be 20CP at level 1.5, the Krabby’s defenseIV must be at least two lower than the Diglett’s Attack IV.
For Poliwag, Diglett must have access to the now-discontinued Mud Shot move. Scratch will not do enough damage to Poliwag. Assuming your Diglett has Mud Shot, any Poliwag that hits 20CP upon Level 1.5 and has a Defense IV no more than 8 above your Diglett’s Attack IV will work.
Remember that the only way to test if your CP20 Bubble-User has the appropriate IVs without potentially breaking Pokemon Go TOS is to actually try them in the Gym and see if they work. Again, if you’re looking to farm appropriate Bubble-users, Horsea will yield the highest percentage, followed by Krabby, and finally Poliwag who won’t even work with a Scratch Diglett.
Test and Execution
First, either take over an enemy gym or level an existing gym up so you can add your Bubble-user in defense.
Next, spam click with all your might.
If your Pokemon have the proper IVs, the Bubble-using Pokemon will get hit with 5 Scratches or 4 Mud Shots and will faint. The word “Victory!” will appear on the screen. If your Diglett’s health bar goes to 0, and it usually will, don’t worry, Diglett didn’t actually faint. The damage from Bubble just visually registered –after- the fight actually took place (hence why you got the word “Victory” across the screen.)
You will have now gained 1000 Prestige for the gym, and 100 personal XP. If there is another higher-level gym defender, he will proceed to demolish your poor Diglett, but again, don’t worry! You still got your XP. Your Diglett will now have 1HP, but this is just fine! Since this strategy does not rely on your Pokemon actually tanking any damage during the fight, a 1HP Diglett does just as well as one with full HP. No revives and no potions necessary!
In addition to being able to powerlevel a gym to level 10 in just a few minutes, this same exercise powerlevels your trainer. Since you get 1 XP for every 10 Prestige you add to a Gym, you now have an infinite source of XP.
Doing this alone can net you a solid XP rate, but manage to gather 9 friends together, and you can all soar in levels at incredible speed. Each of you, armed with your Glass Cannon Digletts and Bubble-users, can stack a Gym full of Bubble-users in just a couple minutes. Then, because your Diglett technically takes no damage in each fight, you can defeat all 10 Bubble-users in the gym, netting 1000XP for your trainer if you beat all 10, in approximately 100-110 seconds. This yields, conservatively speaking, a rate of 32,700 XP per hour, or 65,000XP per hour with a lucky egg active. This alone allows for a gain of over 1.5 million XP in 24 hours, more than has ever been accomplished by a fair-play non-botting trainer.
Source: Pokemon GO- Gamepress