Standard box dye uses 20v developer/peroxide which ensbles a little bit of lift for the general publics use. You do not need the lifting process & need deposit only. For a 30 min dying process total, the first 10 mins lift, the next 10 deposit the color & the last 10 stabalize. The first 10 open your cuticle making the color easy to fade quicker.
Mix up your color as usual & let it oxidise(sit in the air) before applying for 8-10 mins. Then apply like normal you should see the formule go from cream colored to a darker color, this means its @ depositing stage which is when you want to get in on your hair. You can time it 25-30mins after you apply it without harm as color stops processing about the 30min frame if you feel its not been on long enough.
You can call around salons & price out a "clear coat" which is a demi, peroxide free coat like a top coat for your nails but for your hair that shouldnt be to pricey & locks in fresh color adding shine!
Good pick! I always tell clients to use L'Oreal if they do a home job because they have a pro line for salon & know their stuff!