Just laid sheet vinyl in my bathroom, a small job in prep for doing bigger kitchen job. I put down a good quality underlayment. From what I read on sites such as this one, you should patch the joints and nail indents and then sand smooth.
The surprise came when I went to sand the patched areas. The patching compound had dried as hard as concrete (in fact I think it was concrete) and I couldn’t sand it. It just wore away the grit on my paper with no noticeable effect on the patch. I was able to scrape and get it to the point where I could lay the vinyl.
Before I do the kitchen, which is a much larger area, I want to make sure I’m using the right patching material. It was Simple Prep Pre-Mixed Floor Patch.
If that’s the right stuff, how the heck do I sand it?
Dude, the pre-mixed floor patch that you are using is supposed to be used to repair holes and cracks in concrete and plywood floors “prior” to installing the new floor not for patching your nail holes in the finished product.
When the patch was still wet you should have cleaned your tools and the patched area with warm soapy water. That stuff dries like cement when not cleaned right away.
You’re out of luck on trying to clean it once its dry...