I'm using WD40 and diesel do clean up everything.
I've never heard about anything like "marvel mystery oil" in Brazil. The penetration oil most common here is WD40 and similar products.
A friend told me that acetone is the best penetration liquid he knows.
Yesterday I tried to search the "dry ice" approach on google. Didn't find.
How do you use dry ice? direct on top of pistons?
I think that as soon as I clean the engine, it will run smooth