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I was apprehensive about Picnic breeding at first but I've been trying to get a shiny Greninja and have been hatching eggs for a day so far and don't think it's terrible. Egg food makes the process better and you can get about 2 full boxes of eggs in about 30 minutes then soft reset of you don't get anything.
This is coming from someone who has hatched a couple eggs the last time it was "easy" to do.