I learned that Pokemon can combine with a person in a process known as "Burst". Apparently the Pokemon are inside a crystal known as a Burst Heart and "one must go through rigorous training or else their life will be in danger if they attempt it".
My question, then, is if the training is Pokemon specific or works for all cases. So if a person has trained to Burst with a Pikachu Burst Heart, could they also Burst with a Geodude? If so, could the person Burst with multiple Pokemon at once?