Lately I have found that a lot of people will not use sandpaper to remove engraved letters on their Apple ii computers. That is because the sandpaper removes the original grain pattern in the plastic.
Others, do not want to bother with RetrObrite, so for those people a technique is still waiting to be discovered.
The only other alternative is to use this technique I have come up with.
Although I have not tried this myself, I would if I had to.
To restore the original grain type finish on plastic, use RustOleum Rippled Effect spray paint.
I discovered this spray paint about 2 years ago.
The grains can be simulated using this paint but it also depends on how well you use it.
So get your messed up plastic and experiment!
Give it a try just for the heck of it.
We can post the results on this thread.
I will post this info on Facebook also.
Here is the website for this unique product:
http://www.rustoleum.com/product-catalog/consumer-brands/specialty/rippled-effect