02Giant 

Any chance of posting a picture of the bike in question?
Your idea should be achievable although likely sacrificing on the color match. I ask about the frame mainly to see what you will be butting up to (vs. blending into) with the existing paint. Assumptions here: the new wont match the old, you need as clean of a breaking point between the old and new, in an inconspicuous location, as it would be extremely difficult to match and blend the two, even for a professional. Do not use 1 part rattle can primer, it makes a crappy base and will not stand up regardless of the top coats used. Use a 2k (2 part in one can, material being applied plus an activator) primer, and a 2k top coat if going single stage for the top coat. The single stage paint has the gloss/clear as part of the mix. If going BC/CC, use a 2k primer, base (color) then a 2k clear. Good prep is the key from dewaxing/degreasing first, the stripping methods, to sand papers, primer application, sanding again, dewaxing again, then on to the finish coats.