Smokescreen and the order of an attack

[Soujiro Elric]

So, I was studying the rulebook and the compendium, and I was trying to understand something. Let's say I have a Reshiram versus a Pokémon who used Smokescreen on Reshiram. Now, Reshiram tries to attack. The compendium says I should first discard the energies, then flip for Smokescreen. In this case, the discard should be the C step of the attack (Do anything the attack requires you to do to use it. For example, you must flip a coin if an attack says “Flip a coin. If tails, this attack does nothing.”).

However, let's say Garchomp C LV.X versus a Scizor Prime. Garchomp has a DCE attached to it. The compendium ruling says that you first choose the energy, then figure out the damage, then discard the energies. Obviously Scizor will not receive the damage, however, in this case, the discard should come after the damage, as part of the effect of the card.

So, in which step do I figure out the discard? C, or as part of the effect of the attack?

[PokePop]

There are two kinds of energy discards.
Requirements and effects.

Requirements have two phrases associated with them:
"In order to" and "or this attack does nothing".

If doing something is accompanied by either of those phrases, then that has to be done before Smokescreen.
If those phrases are not there, then it is an effect and you don't discard until after damage is done, or not at all if Smokescreen stops the attack from working.

[PokePop]

Also note, if Blue Flare's discard was a requirement, then Zoroark's Foul Play would not get to ignore it if it had no Fire Energy attached!