Judging from the picture, I'd say .. neither!~

Clean it and spray a couple of coats of the white primer. If you get that on pretty smooth, you shouldn't really need to do any sanding.
The next day (if the Duplicolor says that soon, sometimes you have to wait 72 hours before continuing)
Spray the 2-3 coats of color, with 1-3 hours between coats. Again, refer to the can.
Spray a coat of clear as coat #4.

Let that dry for the 72 hours at least.

Scuff with red ScotchBrite pads & water.

Clean with water or DX330, not alcohol or other chemicals. water is just fine though. Be sure to get all the nooks & crannies. I use an old soft toothbrush.

Aplly decals if desired.

Dust with a tack cloth.

Spray 3-4 coats of clear, same as you did the color.

Let dry until you can't make an impression with your fingernail. Test somewhere like the dropout where the axle is going to go.

If you are ever in doubt, do a test piece on some old PVC pipe first.