When doing initial prototyping and you don't have any (or little) hand written code you can easily change in the model and re-generate. When you have hand written code you start with using the refactoring tools in the IDE, as you are used to. Thereafter you do corresponding change in the model and re-generate.
Eventual mistakes will normally be caught by the compiler and JUnit tests.
The following screencast illustrates how to rename Planet to Planet2.
Alternative video format (mpg)
Sculptor doesn't make it more difficult to do refactoring. Sometimes it makes refactoring easier, when the change only affects generated code.