i've been using the technique that wayne has explained for a while now. i've had great results for very little cost up front. here are some i just did.
i will add this. i use some white decal paper that's not the greatest in covering over a dark color so i take a piece of unprinted paper and cut an exact duplicate in size and put it down first. let it dry and then i put the color decal on top. here are the results on an obviously dark blue car.
oh, and just so nobody calls the lawyers, i got permission to duplicate this logo..............honest.