Does the coconut oil trick work?

Yes, coconut oil can prevent bleach damage and pain but I don't think 10 mins is long enough.  I usually do a minimum of 1 hour. Also do not rinse it out or it won't work as effectively.
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It needs to be left on the hair, not rinsed off. You apply the bleach (or oxidative dye) straight over the top. It has made bleaching much less painful for my daughters sensitive scalp, before we started using coconut oil she would be in tears every time we did her roots.

I've also experienced that coconut oil really does protect the hair from too much bleach damage, and with my mid-length hair, I try to leave it on overnight.  If you can spare it, I'd say a good amount of time to utilise its protecting powers is 2 hours, then apply the bleach straight on.

Though as I've read and tried to put on loads of the stuff till my hair is dripping wet with oil, it still seems to do the trick (with not as much mess!) to use a bit less and just make sure all the strands are well-coated.

Another yes, seems to work for me. Coconut oil is fantastic - you can use it so so many different things.

I leave it on overnight where possible. I'm usually pretty cautious with bleach anyway, but I've never had any damage when using coconut oil