The diarrhea may last into the late afternoon. I think it depends on how toxic your body is. The burning is toxins coming out. You can wash gently and put some olive oil on your butt to protect it.
Each time you do a Liver Flush it cleanses different parts of your liver. If your liver is congested, that could be why you are not getting as many stones out. Also, if you had solid bowel movements there could have been stones hiding in there.