I've had these highlights for about 3 months now and have done a root touch up once. The root touch up was a breeze compared to the initial highlights (although digging through my hair to find EACH individual highlight and separating it out was cumbersome).
Going into this I knew I didn't want a lot of highlights/color. I am not a fan of white/light blonde strips of hair against dark hair look and I just wanted a few dark blonde/warm brown pieces for spring/summer.
First I put on old clothes that I wouldn't mind getting bleach on. I also wait at least 2 days of not showering before bleaching or coloring. My skin/scalp is sensitive and when I wait, I have almost zero reaction to bleach or color. The natural oils on my scalp protect my skin from being harmed. I have colored my hair 12 hours after a shower and my scalp itched/burned- never again. Also, foiling the highlights is better for me because I can cover some gray hair without directly having the bleach/color on my scalp.
I used regular ol' tin foil and folded it so there was a solid edge. I made about 10 folded foils (each foil holds about 2-3 "highlights" or separate pieces of hair). Once that was prepped, I mixed my bleach and developer. I wove a rat tail comb in between my hair to pick up small sections of brown hair. I placed the foil underneath and then applied the bleach with a bleach tint brush. Then I folded the foil and moved on to another piece. I only colored pieces in the front of my hair and did NOT highlight any right on my hair line (sometimes this creates a look of missing hair if the rest of your hair is dark). My highlights started at least 3/4 of an inch from my hair line and have created a very natural looking highlight (when my hair is in a pony tail it looks really subtle- not like skunk stripes).
If a piece or two over processed (causing it to be lighter than the other highlights) I went back a few days later and colored those pieces with a demi-permanent creme hair color with no ammonia (I used Ion in 7NB Medium Neutral Blonde) to tone it down.
The first two photos are right after I highlighted my hair for the first time. I am still in my "bleach" clothes :)
Below are pictures of what I use and also of my hair about 3 weeks after my last touch up (I also added 4 new full size highlights). I keep all my supplies in an old box up high on a dresser where Athan cannot reach them- in the black plastic bag: gloves and extra hair clips are in the clear plastic bag.
This last picture is how I part my hair 90% of the time. I love the highlights on this side.
For root touch up, I use foils but they are really small. I just apply bleach to the regrowth and NOT to the already bleached part. Fold them up and process.
Each person's hair is different so processing time can be drastically different person to person. I did a few test strands with different level developers and timed them to see how long the highlights should stay processing before rinsing.
This is my first spring doing my own highlights and it has been fun so far. I had very light blonde hair for a little over a year so I knew which products to use for my hair and which ones not to. I don't recommend anyone to do this at home. This post is not intended to provide any kind of advice, but just reveals what I have done.