I have read many confessions on this site from men who desire to service another man orally, but say they don't know how to make it happen. I wish I knew how to contact them; I'd love to have my manhood serviced by them and maybe even return the favor. I'd say, just offer your services. I know it's scary not knowing what reaction you will get, but the odds are in your favor. Generally, guys don't pass on the opportunity to get serviced, so just go for it.