Andrew remained in seclusion for three months after absorbing the light-type divinity. Unlike the one he had absorbed before, this time Andrew didn't need training to familiarize himself, which is why it took so long.
Simply put, Andrew controlled his new divinity through meditation and mental simulation training. Normally, this isn't possible; not even an expert's energy boost could do this, much less a divinity, but Andrew is a special case.
The reason no one else can do this is that the power they acquire is greater than their existence. Simply put, when an expert increases their power, their body and soul are barely at the entry point.
This means that they barely meet the minimum requirement for this new power, so they must train and condition their physique and spirit to master it, so meditation and mental training aren't enough.
