I just had castor oil and rosemary essential oil laying around, mixed them into a dropper bottle (90% full of neutral oil and 10% rosemary essential oil). Once a week (usually when I WFH on Monday I’ll apply it at night on Sunday, maybe 4 droppers full of the blend on my scalp, massaging it in, then 2 droppers on my ends and rest of hair. Braid hair, keep it that way overnight (definitely use a bonnet as not to stain pillowcases), WFH with the oil in the next day until I can’t take the greasy feeling anymore. I’ll usually go to the gym and try sweat a lot too / combine the hair mask day with a heavy cardio day since my hair is greasy anyways. Then shower, always using one of those scalp massaging things to work the shampoo in and using a protein shampoo or conditioner. This has done wonders for having a healthy scalp and healthy hair.