It sounds like you did a thorough and careful job restoring the cutter blade on your 3-in-1 machine. Your method of using a coarse file and progressively finer tools to maintain the original bevel and remove the knicks seems effective, especially given the constraints of not having a lathe. It's great to hear you didn't need to use a grinder, as they can sometimes introduce heat damage if not used carefully. Your perseverance paid off with a functional and keen-edged tool.
For the skiving blade, you might find a similar approach works well. Starting with ensuring the blade is securely held, you can use the same progression of files and stones. Keeping the bevel consistent is crucial, and frequent cleaning during the process will help you achieve a clean, sharp edge without introducing unevenness.
Lastly, documenting your process with photos next time could be helpful for sharing your success and techniques with others who might face similar challenges. It might also give you a good point of reference for future projects. Good luck with the skiving blade, and kudos on reviving your 3-in-1!😊