Gold bottle cap questions

I have a few questions with the gold bottle cap, I have used a silver one but never a gold one:

1. Have you used it on a Pokémon with a LOT to upgrade and is it possible in a year without sweating too much?

2. Would you use it on your favorite Pokémon (Heracross) or a very usable one (Shiny Ray with DA). I have a non shiny Heracross that is 15/14/15 and two non shiny Rayquazas that is 15/15/14 and 15/15/13 if that would affect your opinion.

I also put some others that I might think about using it on.