Paper towel after jpmcwjr was the first to recommend it to me a when I joined the forums. If I get an estate pipe, I very carefully use my knife for the bulk, then I dissolve some with alcohol, and use though tough blue shop towels to remove more. I have been known to use sand paper/scotch-brite pad to remove even more if I question the integrity of an old pipe or have to remove the cake completely....though I'm as careful as I can be...probably wouldn't do this but the Butner-style I bought from P&C matched it price...horrible...thinking I need to invest in the Castleford. Unfortunately when I had the money, I looked and couldn't find any in stock.
I will say, if you are scraping your pipes....be consistent and as even as possible. It's been recommended by others to hold the blade perpendicular to the bowl...Dulls up a knife fast, but before I started doing that I took a bit of the rim off of a pipe by an accidentally slip. Lessons learned in the beginning usually stick the longest