Using the trainer it is simple. Select the character (make him active). This has to happen outside of camp when you can physically choose each character.
At this time, you can use the trainer to increase attributes, skills or abilities.
The runscript dbg_setattrib command only gives a 180 second buff to the attribute, not really what any of us are looking for. Although, it does allow you to equip items you cannot equip normally. Just don't take them off.