Don't scrap off all the paint. Espically if your frame is
aluminium. Once you soray off all the paint, and your frame
oxidised, your paint will be less hardly. Scrap off abit, but not
all of the original paintwork.
If your new coat of paint is dark, don't bother with spraying a
layer of white paint. The white base is such that you can paint
other colors on more easily, but if you are spraying on dark
colors, y bother?
The trasparent layer is ayrlic(spelling?) lacquer. It's not very
helpful, just another layer of protection. Another suggestion is to
go down to a car spray shop and get them to lacquer it for u.