Actually you wetsand them with 1,500g sandpaper, clean them really good with wax and grease remover, then add a touch of black in your clearcoat and depending how dark you want them depends on how many passes you make with the clear. Also there isn't just black, most black toners (paint) are blue based black or brown based black, I'm guessing VHT's is blue based black due to them turning blue'ish, and I guessing that that is with the lighter coats/shade. The more coats/passes the darker and the blue'ish tint shouldn't be noticed.
I did my 3rd brake light, came out good.
Or just take them to a good paint and body shop and they should do it pretty cheap.
I personally would stay away from VHT or anything in a shaker can.