I sharpened up my Harbor Freight machete last weekend. I'd never had a decent edge on it, so I first used a couple Nicolson files. The first one was meant for rapid metal removal. I then used a Bastard file menat for gradual metal removal to smooth up the edge.
Next, I taped a mousepad to my workbench, then taped a piece of 150 grit sandpaper on top of it. I used this to finish the edge. I mostly moved the blade on the sandpaper away from the edge, like stropping it. I did do a few strokes of the blade forward on the paper to make sure I didn't have a wire edge. This gave me a convex edge.
I tested it in my yard where I did a bunch of pruning of softwood trees, some forsythia, and some nettles encroaching onto my property from the neighbor in back of me. It cut very well and the edge was still sharp after about an hour of whacking things.