I have a bunch of Pokemon that I need to get to level 100 so I can hyper train them and killing Chanseys and Blisseys is so annoying because the exp gain gets lower the higher the level of my Pokemon is. Pokepelago is even slower because it only adds one or two levels and that takes an entire day. So my questions are:
The fastest way is by using Rare Candies or the equivalent (and multi-pack versions) available from Rare Kitchens in Festival Plaza, provided you have enough of those to bridge the gap from the current level all the way to 100. (You can also buy Rare Candies at the various beaches for 48 BP each, but that's not a very efficient use of BP.)
If you don't have enough, you're stuck using the various battles for their experience yields, which diminish as you get closer. The best sources available are Chansey chains (level 54-57) and repeat trips through the league (level 66-70), which are slow progress as you get into the 90s but still faster than anything else.
