How can I lighten my hair evenly?

I'll start off with saying, you don't want to use 40 vol ever, let alone if you only want to lift a couple of levels. The higher the volume the peroxide is, the faster it makes the bleach work. 40 volume is only for use away from the scalp and on very, very dark, hard to lift hair (and even then I wouldn't suggest it). The most I would think you need is 10 vol, so 20 would be better to allow for the booster. I don't know if it's true that the booster dilutes the peroxide, so I can't comment, but at least 20 vol is easier to control than 40 vol. 40 vol will work far too quickly for what you want to do, and how long it's going to take. You'll end up with white, heavily damaged hair in the area you start!

Don't start with your ends. They're already dyed and therefore don't need much lifting and they're damaged, the longer the bleach is on the more it damages. The hair at your roots is going to lift faster, but it still has further to go. The already bleached/dyed hair will lift quite fast. So do the highlights at the roots first. What would be best is to do it at separate times. Do your roots one day, wait a few and then do the ends. That way you have less stress trying to get both done in one go. You also know what you're aiming for as the roots are already done.

I'll also add, be ready to have to bleach all your roots. Baby highlights aren't easy, but especially at the roots! By all means try it, but be ready for it to go wrong... always, when doing your hair at home, have a second option you can go to in case it doesn't come out as you hope. If you aren't happy to do that, leave it until you can go to the salon!

I hope I've understood everything you said, it's not all that easy with no reference photo 🙂

thank you for the response!!
about the boosters, they say if you use more than 1/8 oz of booster with a 2 oz bleach mixture then you need to use the next up developer... but i’ll take your word for it because the prospect of using 40 vol was definitely unnerving.
the babylights method i was going to do was to weave and foil, ive practiced with the weaving and foil to be more comfortable with the technique and im hoping it’ll turn out well. so you think 10 vol will be enough to lift those strands to a level 8 or so?
and i was wondering if i should do a bleach bath for the ends since they don’t need to be lightened much and to be less damaging... what do you think?
i’ll reply with a photo of what my hair looks like now, it’s a bit more grown out at the roots though. sorry for the photo too this was the best i could find that really showed it 😂
thank you so much! <3

sorry for the photo this is the best i could find that showed it 😂 roots are a bit more grown out this was a little over a month ago

The reason it's so hard is trying to do anything at the crown and back of the head. It ends up taking quite a lot of time as you're having to check mirrors etc (and even more reason to use low vol peroxide!). Added to that you're just doing the roots that way, it gets pretty tricky!

One thing I should have added, do a strand test. Ether with hair from a hairbrush or in an area of hair that stays hidden. See how long it takes to lift to the colour you want, on the previously died hair and the roots. That will save a lot of headaches.

I think you might need to go with 20 vol as your roots are a little darker than I imagined, but again, that's something to work out with a strand test. Even though I did hairdressing and learnt all the terms, imagining what level hair is just isn't something I'm good at! As you're not aiming to go more than a few levels I don't think you'll need 30 vol. My hair is darker than yours by at least a couple of levels and I get to level 8 or 9 with 30 vol and a good bleach.

I think you're right that a bleach bath is all you need for the rest 🙂

Thank you so much Janine! I'll do a strand test per your recommendation. You've been a great help. I'll let you know the final result!! 🙂