Reply by Andre

Yes , you need a oil stone or a Water stone or a diamond stone in the 2000 to 8000 range. Heard of some folks using sand paper but never seen or even considered trying it:) Suppose if the blade is not to bad could strop it with some compound, but if you took a file to it way too late? A spoke shave blade should be able to shave the hair off your arm!
For what you want to do perhaps a draw knife would work better? Still needs to be sharp!

-- Lifting one end of the plank.