Never blast at a 90 deg angle.Always keep the blaster at a good slant to the panel. I use a tecnique I call wafting,where the blaster is kept a fair ways away from the panel and never stays in one place too long.
Here is a great hint for you if you want to use sand.Dont! Buy glass grit and use it. It cuts much faster and will reduce heat in the panel as a result.
