I have it emptied and tried scraping it with a sharp screwdriver and steel wool but a a bunch of yellow crud is still caked on. Any tips?

Scraping the sides usually works for me. I do it while the pot is still hot. 

Just had mine block up terminally. Poured out the lead then scraped the sides and did my best with drill bits and bits of wire trying to clear the spout. Not sure I wouldn't be better off using a ladle and abandoning the spout. Will give it one more chance!

Penicillin should clear it right up. 

Wire drill brush works but I am getting tired of the constant clogging.  Right now I am using a small ladle that was like  $6 and it pours great. 

 

Allen 

You need to degas or flux the lead when it's at melt temperature, paraffin or bee's wax works good. The yellow stuff would be sulphur from poor quality or plumbers lead. After the wax burns off,  ladle (old table spoon) to to remove the floating debrise, the lead should clean and your pot will stay clean if you do this every pot load of lead. My Lee's lead pot is over 40 years old and works good.

Tom

Funny you should say that. All my lead is 100 year old lead pipes I take out of houses when upgrading plumbing systems.