How did the African-Americans escape detection on the Underground Railroad?

The Underground Railroad helped slaves escape from the South prior to the Civil War into the North and Canada.

I am just wondering how they were able to do that, especially since racism was rampant back then, and a group of traveling African-Americans in the South would be suspected to be escaped slaves. (Especially after Dred Scott. There were actually bounty hunters going after escaped slaves.)

How did the African-Americans who escaped slavery manage to escape detection on the Underground Railroad?

P.S. I read the wiki article already, but it covered mostly the history and procedures on the Underground Railroad, not so much what the actual experience was like.