I personally use maybe 2-4 tablespoons of baking soda, in about 1-1.5 cups of water. I don't have exact measurements since I just eyeball it and know how much I need, but I feel like those measurements are pretty close to what I use. Looks like our hair is roughly the same length, so that should be enough mixture. Wet your hair first with plan water from the shower, then use that mixture and very gently ''rub'' it into your hair all over. I'm not talking anything like rubbing like you would with shampoo, but just very gently so that you can help mix the BS/water mixture throughout the hair better.Leave it in for a minute or two then wash it out, making sure you rinse it thoroughly to not leave any baking soda remaining.