(OPTION A) Wet your armpits and try to use a very small amount of coconut oil and baking soda. Rub the hairs between your fingers. massage the armpit. Apply enough to allow to dry somewhat and not be to gritty/greasy. Coconut oil neutralizes odors very well. Wear t-shirts to ensure oil doesn't get to clothes.
(OPTION B) You may have low porosity. Where your cuticles won't open. Everything sits on your hair and never penetrates. This is a real problem, especially if the hair isn't moisturized at all. Buy a good clarifying shampoo, sulfate free and moisturizing. Shampoo your armpit hairs, rubbing your hairs between your fingers, till you feel the weight of the water in your hairs and buildup gone*** Oils like coconut oil can penetrate/deep condition if left on for a few hours in these cases. Heating the oil will speed up the process as well. Rinse after a few hours and shower. Apply regular deodorant. STAY AWAY from anti-prespirants--they intensify the low porosity/no moisture problem 10 fold!!!