Been trying to research scraping a vertical surface and could not find anything but a special vertically mounted granite surface plate. I have a mill I want to inspect and possibly scrape if I have to.
The information you are looking for is in the machine renovation "bible", Machine Tool Reconditioning, by Edward Connelly. You can find it here on this site:
http://www.hobby-machinist.com/threads/connelly-on-machine-tool-reconditioning.41802/
That said, I suggest strongly that you do not start out learning to scrape and rehab a mill by reading part of the book and getting on with it. You will not be very likely to have great results doing it in that way. It is a bit like a guy who has never held a screwdriver in his hand, and has a plan to completely rebuild the engine and transmission of his car, including all the machine work, all as part of his first project and by himself. It isn't likely to turn out well.
I do recommend you read the book and make sure you understand how to properly test and assess your mill's current condition, and read and understand the sequence of operations used to get the geometry of a mill back to flat, square, and parallel like it left the factory. Hint, that sequence is almost certainly not what you think it is. After getting an understanding of the process and how to prepare for the job, then make sure you are up to the renovating task, which can be long and difficult at times, and even more so for someone new to the work, who WILL make mistakes.
The best bet is to find someone who has a lot of real world experience with doing this work and try to get him or her to mentor you for the project.
It is far better not to start rehabbing the machine at all if you are not truly up to doing the learning and hard work required to complete the job to a proper result. That usually ends with frustration followed by a basket case sale.
Machines do not need to be perfect to do very high quality work.
Scraping vertical surfaces is not required, and should be avoided if at all possible.