I now use Microsoft Publisher to print. I've also used Photoshop and Word. The Testors kit comes with a limited program which will allow you to import and place your graphic on a template to fit the paper. It's okay but with Publisher I can get more graphics closer together and conserve paper.
I haven't ordered from decalpaper.com yet but their prices are much better per square inch. They also carry the laser paper which doesn't require a fixative.
Word of caution on appling the fixative spray...start off with a light spray.
Too heavy and your decal will bleed like a stuck pig.
Only soak the decal untill it will start to slide off the paper.Wetting your blank aid in positioning your decal.
Run test prints of various sizes of you graphic on plain paper to test for wrap and viewability on the blank.