Tire paint will never make the letters look new or original again. The small cracks (from dry rot) need to be removed or dirt and discoloration will always plague them. Painting over the small dry rot cracks and rubber oxidation would be similar to painting over pitted or deeply scratched metal. It will always be detectible. I have used the sanding process on every NOS tire I have and they look absolutely new when they are complete. I have an NOS tire that I have not detailed yet. I will post a picture of two side by side letters to show the results. One letter will be sanded and the other will be in 40 year old, untouched condition.