How can you do at home root touch up without leaving a weird mark in your hair?

If you use an at home root touch up kit, does it ever overlap the existing color and cause a weird break line or is it mostly undetectable. I don't want my hair to break off at a weak points way on top of my hair or something bizarre like that. But I want to bleach at home and maintain it with over the counter box kits. Is that a good or bad idea?

you would defiantly have to have someone help you, you can't see the back of your head, and you would want to be able to put it on fast, & not overlap, that is is the main thing no overlapping, even some professionals will overlap bad thing to do, over time it will weaken your hair and sometimes where you overlap at the color will be a bit different, depending on what you are using. In something with bleach I would say go to a salon or beauty school

bad idea bad bad bad.. and i dont even no why