EagerRhino

Use map pokes if your pokemon is lvl 100 to even out its exp if its an odd number like 1,3,5,7,9 because all map pokes are guaranteed specific exp based on their lvl. If your pokemon has even amount of exp like 300,002 for example then battle a pokemon with 2 of your pokes, the exp reward is usually in an odd amount.

This is pretty much what i do and how i got my arceus waters  to 50,000 base exp and even a more challenging all same numbers like 1,111,111. The same number exp trick is a forgotten relic in the vortex history.