I think if you were to paint it then it would be trying to paint thin strands which could be difficult, the other option would be to model it using a thin blob of GS and a pin to give it the desired texture, if you mix Vaseline into the GS then it won't stick to the model as much and can be pulled off if it goes wrong,you can glue it on if it does go right
Maybe not much help I'm afraid, I don't think glazing would work well, it would look like he shaved his chest and it is regrowing, drybrushing might work but I'm not certain, something my brother in law used to do when he collected warhammer as a teen was add some superglue to some paint then pull it to make strands of hair, I've never tried it myself though but supposedly it used to work