If the razor blade is parallel to the plastic it is very likely to dig in and gouge the surface. The photo does show the razor laid flat, but I have found the best method to scrape that layer of oxidation off is to hold the razor blade almost a perfect 90 degrees from the panel.
a gentle trim on the corners of the razor blade may help prevent gouging. when you sand, may i suggest using the same technique as when restoring stainless? sand in a given grit in one direction only. when you switch to a finer grit, sand perpendicular to the previous direction, until scratches from previous grit are gone, then switch to next finer grade, back to original direction etc. until reaching that 1000 grit. lots of water is your friend..that technique should result in the least amount of sanding, and provide some indication of your actual progress.
That's a good tip on the sanding angles. On a few of these parts it would be quite tricky to switch directions with each grit, but knowing it would speed up the process does make it worth the inconvenience.
Great article Kyle & Kudo's to you for all your hard work! Now, after all that said hard work, if you are going to ride this bike as hard as you say you are....do yourself a BIG favour. Being that the original plastics are VERY hard & brittle (don't bend much w/o ending up broken or at least with the big white crease line where bent), go and buy some Preston Petty or Cycle Am aftermarket pieces (Fenders/side plates are what I am talking about).They are not very expensive & will take ALL the abuse you can give them w/o previously said damage. Then, when you are ready to sell the bike, remove them & replace with the (near Factory) 1's you have re-done & PRESTO, your bike looks A..kickin.. & brings in enuff $ (hopefully) to compensate for the A/M parts! 🙂
I would replace the plastics, but replacements for the XR are actually quite tricky to find and not cheap when available. I have a Maier rear fender on the way because the original is cracked and my previous repair didn't hold up very well, but at $65 for the cheapest version I wouldn't call it cheap. The side panels are each over $100. For what I am doing with this machine, this (not so) quick restoration is perfectly presentable.