Anything Sharpie can do, I can do almost as well
Chain guard off, chain thoroughly cleaned with Motul Chain Cleaner and a worm chain brush, makes fairly easy work of it.
Amazing the amount of crud that get washed off with the chain cleaner and worm scrubbing brush.
Blasted it off with compressed air after drying it with a rag, leaving it for a while to completely evaporate the cleaner before lubing it with Motul C2.
Chain adjusted so that the chain just touches the lower swinging arm guide when pushed up in the tightest point on the chain run.
Apparently one of the best test to find out how much your chain has worn is to clean the chain and adjust the chain correctly then grab the chain at the centre off the rear sprocket and pull the chain out directly backwards away from the front sprocket if you can push a pencil (5 to 6mm) between the chain and the dell in the rear sprocket your chain has just about reached the end of its life.
Mine pulls out less than 2mm, so all good for a year or three.