In the past I did experiment with merging, and it was a process quite similar to classic forcing where I was sitting and thinking about personality traits, but with the intention of the resulting identity to identify with all the parts that I wanted to merge.
Most of the time it was actually resulting with A+B=C, which looking at it now I don't consider to be an actual merge, but a new identity that identifies with the parts that make it.
When after long process of treating DID I first experienced final fusion, it shocked me how it felt, because noone really explained what it feels like in the community; I remember I did share it here when that happened.
Basically, I just felt that all the experiences I've had, everything I've done, were experienced and done by... me. I always thought after fusing I would feel that some memories would feel like they belonged to specific identity, but all of that was gone. It's like those memories are mine and mine alone, and in a strange way they felt like they have always been.
Those moments of fusion were for a few hours, days or weeks, but unfortunately they weren't stable, because the things that were causing dissociation of identities were still there, so with subtle stress I was falling apart again. But having just those few experiences were enough for me to be excited about full fusion.
How I experience integration now? So just to present how it feels, I integrated Leiko and Kitkat yesterday and represent it now.
They've always had very different personalities and before I experienced fusion it was hard for me to understand or predict what their fusion would even result with. I had no idea what resulting personality would be like.