You can stop kiss by just typing /end on your main guy. You may also need to type /melee off which will turn off mq2melee if that is running.
Then your second toon can target the first toon and type /mac kissassist assist
Now you can focus on getting your other guy setup and automated well. But some day when you have time, you should work on getting the main toon set up with kiss as well. Because you can set it to do as much or as little as you want. I like to still play the main toon, so I manually run around and pull stuff to group, but then when I hit auto attack it can do the taunting and defensives and stuff automatically. It is really nice. But yeah for now, /end will stop kiss completely.