Q&A: Modifying a quick refreshing scalp spray – part one, altering the ingredients (formula)

In the Q&A post, Tiba asked, I’d like to ask about salicylic acid toners. I want to make a toner that decreases oiliness of scalp, sprayed 10-15 minutes before bath time on scalp. My only experience with formulating is making Salicylic acid with ethanol 99% (absolute alcohol), TCA (?) with purified water. But for the scalp…