Best way to level up Pokémon in LGPE?

Question

Specifically for leveling up Mewtwo and Melmetal

Answer 1

Basically, the higher your combo is, the higher your experience multiplier is. It actually gets a bit ridiculous after a while. I was pulling 21,500 experience points a catch over the weekend just from lobbing Ultra Balls at unsuspecting Rhydon in a late-game area. I got 10 Pokemon to level 100 in a few hours – granted, four of those were already 75+, but it’s still an impressive feat if that’s the kind of feat you’re inclined to find impressive.
Ideally, you want to find an area in which the Pokemon are a high enough level for you to earn more than 62 experience points a catch. I use Cerulean Cave usually (home to Mewtwo), but places like Victory Road and the Seafoam Islands work fine, too. There are also exceptions for Pokemon that are known for being rarer/having better stats, such as the Tauros that roam to the right of Fuchsia City. Just pick somewhere with decently-leveled Pokemon that you like and don’t mind catching 100 of, because you’re probably going to catch 200.
The aim is to stack as many multipliers as possible. The catch combos add one multiplier, but you also get multipliers for size, throw, and technique. If you catch a Pokemon that’s bigger or smaller than any of the Pokemon of that kind that you’ve caught before, multiply. If you get an excellent throw on the first throw and used the motion control to gain the “technique” bonus, multiply by loads. You get the drift.
Aim for huge or tiny Pokemon (they’re worth more EXP each) and try to catch them with a single excellent throw. If they break free, you’re better off without them anyway. Another Pokemon will appreciate you for who you are and get cosy in the first Ultra Ball you throw. (Ultra Balls are still for Tories, by the way, but Poke Balls don’t really work against big and strong Pokemon. Rob them from the in-game Tories – you can literally find Ultra Balls all over the floor in Cerulean Cave – and use them out of sheer spite.)

I've seen my friend do this and he did do it fast. I just asked him and he gave the source. Check the source for more info!
Hope I Helped!

source

Comments

The best Pokémon to catch for this is Chansey.

Also, you get a bonus if you sync your throw with another player, so have one “player” (you will be the only one doing this, of course) have an ultra ball and one “player” with a regular Pokéball (catch rates don’t stack). Throw them both at the same time, and there you go.