How do you get...

Unfortunately I don't I am at work right now and I noticed a white streak mark (almost looks like a chalk like) on the handle of the horsebit. Darn it I wish I was able to post of picture right now but I can't.
 
Are you possibly talking about DEODERANT marks?

You can remove deoderant marks by rubbing it with plain fabric. let the fabric grab the deodearant off. Whatever you do, dont use water.