Re How To polish horns

What should I use to polish my steers horns they are black

Same thing you use to polish his feet. 

Sand paper and steel wool then oil them at the show

And is there  a right shampoo to use? I have just been using baby shampoo.

I had a heifer with scurs and we used fingernail polish to make them blacker and more shiny. I'm not sure how well this would work with bigger horns. I have also used shoe polish. I would think that a hoof treatment might work well too since hoof and horn proteins are the same.

Um... A pair of dehorners?

hacksaw lol

Haydog, I believe that you are a beginner so I am going to ask how big are these horns you are worried about polishing?  I suggest you check the rules of your target show because in a lot of cases there are rules banning any steers with horns or scurs over a certain length which in many cases is in the range of two inches.