Yes, I just cut and paste the content into another page. If it is template content then I usually cut and paste it into a new template (something like Template:<myTestTemplateName>). I usually forget but it is a good idea to put a comment in the summary text field to say where it came from. As you mentioned, other content is easily to cut and paste into your sandbox.
Good idea for the AnswerBox template. There is a Template:Self Assessment that has a slightly different method for providing feedback.