I agree re the water-soluble marker. Apart from being thinner than a pencil, it also doesn't scratch the plastic. I've got a CRP1 which has had a few years of good useage (yes, I really do still use it!), and a CRP5 which has been put through the ATPL exams, and both are as good as the day I bought them.
(Only problem with the water-soluble pen is the black mark it leaves on your hands when you wet your finger to wipe it off!)
FFF
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