I once did a German style spiral on a Dubro spinner using Perfect Paint. I tried masking and all that but it just didn't work too well until I did the following... I cleaned the spinner with denatured alcohol to ensure I had a very clean, oil free surface. I then took a scotch brite pad and just roughened it up a tad to give it some bite and then wiped it down again (while wearing gloves). I painted the whole spinner with the spiral color (white) and let dry. Then came the "fun" part, masking off the spiral. I placed a small masking tape circle over the tip and then using 1/16" chart pak tape, I started making a spiral to the base. I then started a second chart pak spiral that got a little farther from the first spiral as it got near the base. When that was done, I started filling in between the two chart pak spirals with Bob Dively's liquid masking film. The stuff dries pretty quickly and I put on about 3 coats to make sure I had full coverage and it was thick enough to peel off without breaking. I then shot on the other color (happened to be black) then peeled off the tape and masking film and there it was... it looked really good.

I'm sure other people have methods they would use but this is what worked for me and it worked really well.