If I am converting a pipe over, the first thing I do is ream the cake out, this gets rid of a lot of ghosts. Then you can try smoking burley blends in it. If it's really bad, the alcohol/salt or alcohol/cotton ball treatment should work. Greg Pease has an article on his site about a pipe that was ghosted so bad that it didn't respond to any of those methods. He finally used charcoal in the bowl and heated it in his oven and cleaned it out. You can read more about it on his website. I never let a lot of cake build up in my pipes and I think that helps hold down on the ghosting problem.
Smokey