I'm having a hard time understanding how using one of the letters you removed helped remove the remaining letters, hence causing your issue?
With all due respect, you need to research a lot before you attempt what it is you're asking. The posted link is a good one but might I also suggest knocking on the door of a body shop and asking for first hand advice.
If your preference is advice online, drop me a PM and I'll forward you Dylan's contact from Adam's Polishes, who's super sharp in all areas automotive paint. The Junkman is another handle you'll learn a lot from. He has several YouTube clips that will help you out.
Start here - http://m.youtube.com/results?q=the%2...28.CpswKMkrfhE
Automotive primer can come in many colors - Duplicate-Color for example offers them in an array - and the dried finish is often not the same color as the application.
Hope this helped.