The easiest way to reduce the shine of a bald head is to apply a mattifying product. Shine exists when the skin produces oil, and oil excretions on a bald head cause the scalp to shine, especially when light reflects off the scalp.
Mattifying cleansers and moisturizers are two products that work together to help reduce shine. People with bald heads need to clean their heads with a mattifying cleanser, followed up with an anti-shine moisturizer. Look for moisturizers with sunscreen, since the scalp is prone to sunburns.
If mattifying cleansers and moisturizers aren't enough, there are specific mattifiers that work to absorb oil, reducing shine. Talcum powder and milk of magnesia are cheaper alternatives to specialty products, working to absorb oil on the scalp. There is flesh-colored talcum powder available for those who don't like the bright white of traditional powder, although it is more costly than regular powder.