Hello.  To address your first question, I have a recipe from Lorraine Massey's "Curly Girl" book.

Take 1 Tablespoon baking soda and 1 cup warm water.
Combine in a spray bottle and shake.  Wet, condition and blot dry hair.  Spray with mix and allow it to sit on the hair for a minute and then rinse with cool water.  Towel dry and style as usual.
The book also says that baking soda will remove heavy product buildup.

Addressing question #2, my hair LOVES olive oil and 100% pure olive oil works just fine.  You do not need extra virgin for hair.  Salad dressings, yes or to dip bread in, yes for hair, no.  I think the main benefit (besides you not feeling pukey) is it's probably cheaper than EV.