When I washed my daughters hair I used a baby brush and gently scrubbing her hair with shampoo to loosen it up. It worked for her and it went away fast
@nouvelleparis you can use olive oil, rub it in her head and let it sit for a bit then brush it all out, bathe her after and brush out the rest. You can also use Vaseline (which worked best for my 4m old) but you have to let it sit for like an hour and bathe first before brushing. There's also coconut oil that works for some babies.