u/Boomdog_

I'm planning to lighten my hair myself for the first time this weekend. I got level 20 developer and Bonding Technology Crème Lightener recommend by Sally's as well as a toner and level 10 developer to go with it. I did a strand test yesterday and it looked great but it lifted to the correct level (level 9) within about 25 minutes. I'm guessing it will take me at least 25 minutes to apply to my whole head. I know I section and start at the back but how do I ensure even results since by the time I finish, the section I started with should be done? I've seen some places say to set separate timers for each section and rinse out each section at different times but I have no idea how I'd logistically rinse one section without completely soaking the rest of my hair thats still processing. If the front/top of my hair gets say 25 min and the back gets maybe 35-40 min will that look drastically different?