Ed,
Once you have printed, sealed, and applied the decal according to the manufacture's directions, you will want to coat the decal with several layers of CA. I have only done a couple of these, but I did about 10 coats of thin CA to build the level enough to hide the edges of the decal, and have suitable tolerances to be able to sand back smooth and polish without risking damaging the decal in the finish process.
For me, I have found that to get the best finished look, I need to start with a nicely finished PR or CA coated surface prior to applying the decal.
Rich