Windows have to be masked before applying Cuprinol to the surrounding timber planking - and up-to-now I have used some thin polythene from 3M.
Someone told me it's possible to get some masking stuff that you paint on - and then afterwards it peels off. That sounds an excellent idea - because it's really difficult to apply the polythene if there is even a breath of wind.
Do you know what the paint-on stuff is and where to get it?