One of the miniature shampoo bottles you get in hotel bathrooms seems to hold a little meths without any problem. It's never leaked and holds less than a tablespoonful, considerably less that the quantity of avgas in the tanks. A small scrap of J cloth works fine for clearing the marker off both the computer and the chart.
Make sure you use meths or some other form of alcohol (e.g. isopropyl alcohol) and not other solvents such as acetone which can seriously ruin your CRP1.
I use fine point Staedtler or Mars Lumocolour overhead projector pens (permanent) which are available in a variety of colours.
Mike