This is how I restored the shine to my 1995 Honda Magna VT250 motorcycle Engine. The first thing that you need to do is wash the cylinder heads with kerosene and car wash liquid to remove all the caked on grime. Next, start the sanding process using a 220 grit wet- sandpaper, and then step up with 400, 600and 1000. Make sure to wear a mask when sanding. Keep the cylinder heads pretty wet when doing it. After sanding, the entire surface should be thoroughly cleaned and ready for buffing. it is important to ensure that they are free of grit or dirt as these will scratch the newly prepared surface. Then buff it off with a buffing wheel although the buffing makes a difference. Make sure to wear a suitable eye protection because particles will be emitted at high speed from the wheel.
The Cooling fins on the bike were oxidized. so I sanded it down with a 220 grit sandpaper then painted them with high temperature engine paint.
Take your time and do a good job.