I have used VHT several times on mice, old PC case fronts. Also duplicolor and other brands few times when wasn't able to get VHT. White is no need, can make black to red for example. When using vinyl dye, no sanding unless you don't want pebbled texture of plastics. Best to just leave it my opinion as it looks more like original manufacture that way. I made some PC case front, with stripe like this, plus logo text on the stripe and there is no thickness build up. Vinyl dyes is much 'thinner' than paint and doesn't build up in that way.
Please, don't forget to wear respirator mask when working with vinyl dye, or your lungs will be melted. Breathing that stuff is really very nasty.