I'd say rebatching is for people with patience and/or time lol
I've done it two ways; in the slow cooker which takes forever, and in the microwave which you have to babysit. I don't mind either once in a while but I'd hate to do it often.
I've noticed the ones I microwave harden up real quick, but not as smooth as you could get otherwise. And depending on the settings you can easily burn your soap.
If you use the slow cooker, again depending on your settings, you can also overcook but it's a better option if you have other things to do in between checking from time to time.