The trick is to mark them so they do show, otherwise you wouldn't want to go to the bother. What needs to happen then is to be able to get rid of them
There are air erasable pens (purple ink, I think)
water erasable pens (blue ink)
Chalk (just brush off, and old toothbrush might help)
Thin slivers of soap
and I find Sewline retractable pencils very useful. The marks are erasable and come in several different colours.