For the record, there's details missing in the OP. What powder and TC cleaning products were used?
What method does the TC DVD show to use to clean the gun?
Bore Butter itself does not cause rust. Leaving the bore dirty or using water or products containing water and then not fully drying the bore before applying Bore Butter can cause rust to form. Humidity can also cause rust and many people simply do not apply enough Bore Butter.
There are plenty of protective products to use and Bore Butter does work just fine for many who would rather not use a runny liquid oil that doesn't stay where it's applied. In a 3 week period it's hard for me to just blame it all on the Bore Butter without more details.