These guys and their machine workshop toys I had to reface my cam journal surfaces to as they were severely chewed (the bed side of the journal was not anywhere near as bad as the journal caps - it was so bad I could jiggle the cam in the bed with the tappets completely backed off). I used a length of pvc pipe and wrapped it in 400 grit wet and dry, then soaked it in oil. I built up the diameter of the pipe until it was close, sat it in the journal and then gently rolled it to dress the bearing faces. Not text book but it was the best way I figured I could get an even finish. I'd also suggest to radius off all the sharp edges in the combustion chambers and polish them up as this will reduce the chance of pre-ignition from carbon build up and help gas charge flows.
p.s. love the carbie jigsaw puzzle, hope the dog didn't swallow the last piece