Temporary fusion requires a Bond stat of 140 or more with the Pokemon, and Permanent fusion requires a Bond stat of 255. Due to system limitations, items cannot be held by a Pokemon when it fuses.
In a temporary fusion, the Pokemon's gender is used. This can be averted if the Pokemon's bond stat is at 250 or more, in which case either the trainer's or Pokemon's gender can be chosen whenever fusion is performed. The command to perform a Temporary fusion is +tempfuse slot<#>. For example: +tempfuse slot2
In a permanent fusion, the choice of gender between the trainer's or the Pokemon's is made only once, at the time of the permanent fusion. The command to perform a Permanent fusion is +permfuse slot<#>. For example: +permfuse slot2. IMPORTANT! Once a Pokemon has been used in a permanent fusion, it is a part of the character forever. There is no way to return that Pokemon to your party as a separate entity.
Temporary fusions can un-fuse by typing +unfuse. This sends the Pokemon back to the trainer's current group, or - if the group is full - back to a slot in a Box. If all Boxes are full, un-fusing is impossible.