Recently dyed some armrests in a 68. Used plain ol' NPD vinyl dye with success. Prep IS important, started by wiping them with liberal quantity of Iso (drugstore) alcohol which takes off any oil from hands. Then, a wash with Dawn detergent. a light scuff with a scotchbrite. Dry with a hair dryer. Just prior to applying dye, wiped them with lacquer thinner and immediately applied a first thin coat. Followed that with light coats-about 3. Used the hairdryer at low speed, keeping it moving, during spraying, as heat stops the applied material from blushing if weather is high humidity. The lacquer thinner and the light scotchbrite, opens the material to promote adhesion.