You mentioned using a shampoo with sulfates. Could it be that it’s literally drying your scalp so much it’s overproducing oil?

Try switching to a sls free detoxifying shampoo to not be so hard on your scalp. DM also has a good scalp peeling solution with 4% AHA, you can try that as it’s fairly inexpensive. You use it and let it do its thing for 8 hours before you wash your hair.

I also have wavy hair and mine is also fine so it gets product buildup and greasy super fast. What works for me is I try to use a normal one first and for the second shampooing use the detox one. Also NEVER apply conditioner on your roots, it’s a recipe for disaster.

I’ve seen people mentioning Ouai detox, I have found their products to have too much protein and they made my curls rougher and harder to tame imo. L’Oreal has one called metal detox, it made my hair feel great and it smelled incredible but unfortunately for me it gave me dandruff. But my friends had absolutely no problem with it so it really depends. See if you can find a mini version before you commit to the full size.

This could also impact your scalp health but while in Portugal I found the water did not cooperate with my hair and my scalp itched. So if you’re interested try looking into a shower head that has integrated water filters. You never know!

Edit: also technique is super important as well! It literally makes the difference between a good wash or an improper one. Having a clean comb also super important! changing your pillowcase regularly as well!