piping written messages is completely different from handwriting, and uses different muscles (which, unlike your handwriting muscles, don't have the "memory" of handwriting -- your muscles actually know how to write from years of repitition and practice). best advice is to approach cake writing like any skill -- you have to practice. fortunately, you don't have to have a cake to practice on -- just a piping bag and a surface that you can pipe onto (and scrap off of so you can re-use your practice icing). a board with wax paper on top or better yet a baking pan in the size that you'll bake a cake in is perfect, since it gives you the approximate proportions of your finished cake. just invert it, and spend some time practicing (kids love this too! heck, if we all learned to write on cakes as children, as we do with handwriting, we'd all be masters at it now!)
trust me, it's worth the practice to be free of transfering, pressing, or using other imperfect tools or methods of getting words on cake.