Painting my Bike Helmet...HELP!!!!!!!!!!!?

I am a pretty advanced airbrusher and looking to get into painting helmets.

I bought a used bike helmet from the salvation army to practice on. It is really a bicycle helmet, not motorcycle. It didn't have that shiny clear coat you see on professional bike helmets. I bought some Dupli-color Paint Shop Finish System paint from my local auto parts store. I did my usual taping of the design and then hit it with two layers of jet black and 3 layers of clear coat.

It doesn't have that professional shine...is this due to the original paint? should I have used a primer?

Here is the big issue. The paint chips really easily. If you were to rub it the wrong way, it chips!! Also when removing the tape, the edges are not sharp at all and sometimes the paint came up with the paint making the helmet look like...well sh*t.

Is the paint I'm using the problem or the existing surface of the helmet? And why is the paint lifting up with the tape? [I used masking tape rather than blue paint tape]

Will I get that professional shine and gloss with the paint I am using now? Given I do all of the correct prep work.

Dupli-Color paint shop finish system

You didn't prep the surface correctly!

Anything that is previously painted needs to be cleaned and primed properly or you will have the results you are experiencing.

To prep - SAND the existing surface with 220 or even Scotchbrite pads (the green ones) to remove any and ALL shine and loose paint.
Wipe it down with alcohol...wipe don't wash!..dampen a cloth or papertowel with alcohol and wipe it until all dust and dirt are gone.
Then choose a primer fitting to the material you are painting on. Latex primers will not work on plastic...(I usually use a cheap spray primer - Krylon or similar)
After you have primed if you notice the surface is not smooth take some 440 grit and buff the primed surface. Use a tack cloth to remove the dust and prime again. Repeat this until you have a smooth surface to airbrush on.
When taping your outline use artist quality tape! all 'masking' tapes are NOT created equal. If you want professional results you have to invest in professional materials.
Also when painting a taped surface make sure you are spraying at a 90degree angle to the surface...straight on!
If you angle your brush even with good tape it is possible to cause the paint to get under the tape.
You might want to check out www.airbrushaction.com
It's a magazine devoted to the airbrushing world.
good luck