it can be done that way but ,all the decal and scren printing people use vector based programs , like illustrator,corel and inkscape (free)
so if you want to get into designing decals (and possibly masks), it only makes sense to stay away from raster programs like Adobe Photoshop, Photoshop Elements, or Paint Shop Pro and Gimp. and learn to use vector based drawing software.
the learning curve is no different between them.