5160 has a bit of chromium. That makes for a tougher blade...and a little bit tougher to hand sand. It should not be extremely more difficult to sand than hardened 1084, though.
Fresh sharp sandpaper used like it were free is the trick to hand sanding. Pre-HT preparation is even more important. If you leave any scratches in the blade before HT, they will be "a bear" to get out after HT. Take the blade to a flawless 400 grit surface before HT and the post-HT sanding will be much easier. Start after HT with 220 grit, BTW.