is there anything you can coat matt paint in to make it washable?

[SY]

I have just painted my walls in crown matt and now everytime the kids touch the walls they leave greasy fingerprints on them that will not wash off. I have looked to see if they do the colour I have in easyclean but they don't. Is there any other way round it.?

[65water]

If you don't mind a bit of a gloss you could go over it with a coat of clear satin sealer.