Quoted from T-800:Maybe he's reading this and can chime in with some details?
Indeed he is!
The Buffy machines are vinyl overlays that have been clearcoated over with DuPont Chromaclear. Like others have suggested, when using a clear vinyl overlay, you will need to paint the playfield white first to get the most vibrant colors. If you have any clear inserts that have colorful art over them you will want to paint those areas white too. On the last one I did I actually painted the playfield white before I installed and leveled my inserts. This kept me from having to tape off every insert and also allowed me to level the inserts with the now white painted surface. I then lightly sand it as smooth as possible being careful not to sand through the white layer. Then the first layer of clear was applied. This clear layer will help level out any imperfections and give the vinyl overlay a nice flat and smooth foundation to adhere to. Then the overlay is applied. Once the overlay is in place I then had it cleared over to protect it. My painter has had really good luck with that type of clear, but whatever you decide to use, be sure to test it on a scrap piece first. You want to make sure the clear does not react with the inks on the vinyl. Also it is important that the first layer be a thin layer. The clear heats up as it drys and if put on too heavy will cause the vinyl to warp. Once the thin layer has cured you can go back and add heaver layers without worry. Hope that helps. If you have any questions, just let me know!