The serum is transported by blood. Hair has no blood traveling to it, only the root. So, unless Bacon shaved his body clean, his hair wouldn't have become invisible, as wouldn't all of the fur on the gorilla.
When Sebastian gets frustrated with himself in the lab, he stands up, walks, turns and beats his fist twice on the table. This is the same thing Kevin Bacon does in Footloose to his VW Beetle when he gets frustrated with the town.