As most furniture painters lament, primer is usually a bright white color, which notoriously shows though the first coat of paint. One of the best tricks is to get the store to tint your primer a darker color. It won't be black, but it will be much easier to get full coverage and still bond well. That being said, there is no reason to use a stain blocking primer with deep black paints and some paints may not need a primer to bond to most woods.