Have you started electrology treatments on your legs? It might be good to know why you are having ingrown hairs and the black spots. The ingrown hairs should NOT be the result you see when you have electrology, but it can happen with waxing and tweezing.
Ingrown hairs are caused by the hair being broken off under the skin, and then not coming back out through the follicle opening. It either enters the skin or something blocks it from coming out of the follicle. The hair is broken off when waxed or tweezed, or from electrology treatments that are not quite done right - either the insertions were not deep enough or not enough current was applied, then the electrologist just pulled the hair out.
The black spots are remnants of the hair structure, but not part of the hair shaft. At the very bottom of the hair shaft and the hair follicle is the papilla. This is usually black and can separate from the hair shaft upon removal. Nothing should be done to get these out - they will slough out on their own. There are different opinions as to whether or not they are the result of poorly given electrology treatments.
Just in case I totally misunderstood, and you are simply looking for a way to diminish ingrown hairs, exfoliate with a washable scubber of some sort. Natural loofahs are NOT good, as they can hold bacteria and result in a staph infection. There are nylon skin scrubbers that can be washed. There are brushes for the skin that can be used wet or dry. There are glycolic products that help exfoliate. If you are only shaving it might be that you are shaving too often.