Check out a company named Hexis at www.Hexis.co.uk. In the world of self adhesive vinyl the thinner it is the more expensive it is as it sticks better and conforms to curves easier. There are a number of film specifically for paint masking and sand blasting. The masking material has an easy peel adhesive and is usually known as applimask or polymask. If you only want to do light surface etch sandblasting then the cheapest black or white vinyl film is very usable but if you want to cut deeper then you will need proper sandblast material that is almost like a thin silicone rubber but your machine will need a new sharp blade and plenty of pressure.