Just to chime in here. I am, as we speak, having my hubcaps painted. I have 2 sets, one set that will match the hardtop color and a second set that will match the exterior when the top is off. I took all the old paint off myself with stripper. But it took a lot of work, patience, and time. I had to do it a couple of times to get to my clean desired state. I also personally spray painted the inside the original color after cleaning and sanding the inside. The insides look perfect.
Then the question of masking. My local paint guy is a perfectionist and will not use the masking stencil any longer since he claims the finished product is not just a straight line. He is going to use the automotive fine line masking tape ( a couple different widths are available). He claims that this 3M tape stretches a little and works very well. He asked me to sand the areas to be painted which I did with 900 paper. I am taking them to him tomorrow to start the job. I will let you know the results.