If you have flaking already in the existing finish, then you'll want to strip the original paint off, otherwise you'll see witness lines of the flaked off spots through the new paint. Aircraft paint stripper works perfectly. Apply in a well ventilated area and don't let the stipper get on your clothes, etc. Let it sit and hose it off. Its that easy.
If the existing finish is fine, just dull or what have you, clean it with some wax/grease remover and apply the new VHT paint directly on it. you'll want to carefully mask off the unpainted area's like the oil cap hole, where the bolt holes are and coil packs go, etc, but for the OEM lettering, go ahead and just paint over it, and take some fine sand paper after it dries and sand off the paint using a sanding block. It'll look like factory.
And no, it doesn't need to be high temp paint.
Enjoy!