x2
-20WhirlwindYour opponent switches the Defending Pokémon with 1 of his or her Benched Pokémon.
BlindsideChoose 1 of your opponent's Pokémon that has any damage counters on it. This attack does 50 damage to that Pokémon. (Don't apply Weakness and Resistance for Benched Pokémon.)
Can Cramorant with the "Lost Provisions" Ability use an attack from a Technical Machine such as TM:Blindside for no energy cost if there are 4 cards in the Lost Zone?
Yes, that will work.
For Mandibuzz's "Blindside" attack, who chooses which of the opponent's Pokemon receives the damage?
The attacking player chooses which of the opponent's Pokemon receives damage from the attack, but remember the opponent's Pokemon must already have damage counters on it first.