I sprayed it white, waited for it to dry over night then sprayed over it with nutural grey. Again obviously this would depend on what you want the concrete to look like. I then cut them down into 80x120mm sections (again obviously this would vary for different scales and personal prefference) I have stuck them down with sticky back tape for now but they easily peal off with no damage. Dont use spray glue as it is not strong enough. You will find the sand paper (being paper and all) may curl up after painting. Make sure you blue tack it down during the spraying stange. Then once all dry just stick it under a weighty book for a day or too to flatten it out! let me know what you think. all comments, good or bad will be greatly appreciated!