Glad to hear they made it!
For the seat post, we spin the post in a lathe and use scotch bright on it as it spins. Then we blast the head of the post and fade the blast into the scotch bright finish.
So, what you can do is use scotch bright on the lower portion of the post to remove any marks/scratches and try to leave the blasted finish alone at the top of the post. Once you are done with the scotch bright, wipe the post down with acetone or de-natured alcohol and apply the decal.
Once the decal is in place use a clean rag with Pledge on it to give it a nice shine.
Let me know if you have any other questions.