Are there certain props to use in certain contests? Or on certain Pokemon? thanks :D
Here's a link to the accessories and how well they work in certain "contest Themes".
If for say the contest is called 'The Colorful' then colorful items will work better such as most of the Fluffs and all the scales.
This other link helps with Visual Appeal in the contest and depending on which Rank what Themes are available thereby determining the best accessories.
Hope this helpes you. :D