I've been trying japanning using asphaltum and am quite happy with the results. I've been re-japanning spokeshaves before attempting planes. In the picture, the top chamfer shave is original (no touch up by me) to give a comparison with the five shaves below that all have been re-japanned. All but the last are Stanleys. The last one is a Cincinnati Tool shave and I had to replace the handles that were missing. The method I have used is described by Todd Hughes & Sean Cullen.