Here is my pre-unrusted shovel.
I steel-wooled it, put in vinegar overnight, sanded it, steel-wooled it again, then used an angle grinder on the back to create a bevel that is very edge-like but not quite an edge.
Here is the steel-wooling.
Here is the new edgy-but-not-an-edge:
Oiling it down with boiled linseed oil:
The completed shovel. Please note that the black stuff is factory paint. I got a lot of little bits of that off but I thought I'd leave the large sections.