Ratio for baking soda (BS) is 1/2 cup BS to 5 cups water. Put in container & shake it well, pour over wet head. This sits on for 10 minutes or more if you want. This is a no scrub method that is great for newly forming dreads. It will exfoliate the scalp all on its own, getting all the scalp crap & stuff out. Now rinse out well. Next you are going to do an Apple Cider Vinegar rinse (ACV). This is to balance back the PH in your hair from using BS. Mix 1 capful of ACV to 5 cups water and pour over head, rinse right away or within one minute max. This is a healthy conditioner also. Unless you have very oily hair and scalp, it should be used each time when doing the BS wash. I did not always use it in the beginning and the BS fried/dried out my hair and it took months to soften it up again, so that is an important step.
I don't know where you live, not on your profile, so I don't know if your water is hard or soft. With hard water, the BS dissolves better if you boil the water first and then mix the BS in. But let it cool off first.
Here is a posting for essential oils by Soaring Eagle: http://www.dreadlockssite.com/forum/topics/essential-oils-for-dreads-and-scalp-health?page=8&commentId=3754945%3AComment%3A1645384&x=1#3754945Comment1645384
For dandruff and a flaky head, don't wash in hot water, make it cooler. Then when you are all done washing and rinsing, finish off with a very cold head rinse, as cold as you can take. Amazingly this will help and stop the dandruff or itches. Do this each time and your scalp will correct itself.
Not all natural soaps are good for dreads, although you would think so. Find out what your friend puts in them, all the ingredients, and then post them here. We will let you know if they are safe for you. Some can over condition the hair due to the natural oils used, some can leave behind a residue. To use a bar, you can either lather it up in your hands and scrub the scalp gently, or you can rub the bar directly on the scalp. When you rinse it out it will run through your sections, cleaning them as it goes. Once dreads are mature, they can be rubbed directly with the bar.
Hope this helps you .....Peace