Looks great, but may I offer up a couple of suggestions?
Try using that engraving bit for your detail work instead of the 1/16th bit. I find that the beveled edge help with the mask removal over a straight edge.
Get a couple coats of white primer down before hitting it with the Rustoleum. I know its paint and primer, but the primer portion just sucks (IMO).
If you have a steadyish hand, the paint pens at hobby lobby/Michaels glide along the edge and just leave the perfect amount of paint, dont press too hard, let the pen and the bevelled edge guide you.
Remember vinyl is expensive, blue painters tape is not, your first steps could have been accomplished with masking tape and a rule.
For future playtime, grab some 2 part epoxy (not the 5 minute kind) and mix in some black paint and use that in the void. I think you may be impressed! If you stain before you carve like you did in this example, the epoxy is an easy cleanup if you pour too much.
Great job, look forward to seeing more posts.