The need for primer
1-minimizes how much paint you need to cover on your finish coat, white will cover over solid primer grey easier than red or other combination of colors
2- It's Lacquer based, so just about any paint will go over it,, where as some paints might pull the existing paint off

Acetone??
IMO, not worth the mess, smell and cost of the acetone,, and will take just as long as sanding alone. Besides you'll have to sand and prime before you paint the white anyway, all you're saving is the micro amount of weight of the existing coat of paint/primer

good luck