You can do it easier than that.
yes get rid of the old stuff.
Get some EPOTEC, as primer / undercoat, its fantastic, and build really well, give a guide coat and then dry sand with 240 and finish with 400 dry.
Put on 3 coats of colour, allowing about 20 mins between coats for them to tack off.
step back and smile..... :lol:
use 2-pac, its easier to get a good finish, if you have a good area to spray in.