I had got a glass door off an entertainment center, the glass is used as a flat and true surface to sharpen chisels and plane irons, after cleaning the glass I just used spray adhesive to attach a sheet of 80 grit sand paper to the glass.
The bench plane I was working on was one my wife bought for me at an antique store, I don't know if it is an antique or just a old tool, but it needed it sole flattened along with the iron sharpened. I used a black marker and put reference lines on the sole of the plane so I could see when the complete sole had been surface. After the whole surface has been flattened with 80 grit I will work my way up through the grits.
Here is the plane after last night's work, I still have more work to do before I can move to the next grit as shown by the 2 spots of marker still showing.