As we will be using both the positive and negative images I decided to cut my masks using a sharp point craft knife, hoping to get a precise edge so I can use both sections from the one cut. It worked very well.
The instructions suggest we use plain paper and cut several masks, keeping a template, as each one can only be used once before discarding. I have some ‘plastic’ paper and am going to try that. I’ve used it before when screen printing and the water based paints come off easily with soap and water, without damaging the template at all. I’m not sure how it will react to oil paints cleaned with vegetable oil but I’ll give it a go. I’ve cut a couple, just in case.