How to effectively/quickly level Illumina routes?

Solution 1:

The Illumina Spots have hidden Pokémon you can photograph for experience after reaching level 2.

For example, Floria Island’s Illumina Spot has 8 different Pokémon species, such as:

a Sylveon asleep in a bush on the right near the start, a Shaymin on top of a cliff after the first Crystabloom, and a Hoothoot that can be found by throwing fruit at a tree near the end of the stage.

Some of these can be found by scanning, while others won’t appear until you use a specific item.