I just posted a new web page on rebuilding and refinishing the fork tubes. You can see this entry on the right hand column and can access it by clicking the 31 BMW R75/5 Fork Rebuild link.
I’m labeling the web pages for this project with the number BMW uses to identify major sub-systems of the R75/5 so you can easily correlate procedures with parts. You can see the numbers on Hucky’s /5 parts page.
Here are some before and after pictures.