It’s important to be careful when you dye the hair. Any excess dye that gets on the base will color the base. So it’s best to go lightly with the dye. But a little on a comb, comb the hair and allow it to dry. If you still need to get it darker then try another application. The key is to go lightly and not put too much on your comb so that it runs down into the base. I don’t know of anything that will clean the knots other than bleaching. You can buy a bleaching kit at your local drug store. Can anyone else comment?