The reality is it's not a big deal. They will buff out and you will hardly see them.
Each can of spray paint is different, even among the same brand/type/color. Getting decent & even flow is pretty much an exercise in futility.
If you want the smoothest possible finish from spray can be prepared to use more paint and time. Just remember most people are not going to notice anyhow. They'll go 'damn nice paint job' but they wont know it's smoother, and a lot wouldn't be able to tell if you had a side-by-side comparison. So why do it? The same reason we overclock and put an sv24 into the glove compartment of an 81 VW rabbit.
One way to do it. (And why I charge triple for it)
<Remember this is all at your own risk. I am not responsible
. Nor am I responsible for damages>
In your case you'll need to remove the paint and primer. Use paint stripper for better results (edit: DO NOT use stripper on plastic parts. It will soften the plastic and may even warp it or melt it.) the can stuff in the auto section will do. Just be sure to wear big rubber gloves and dispose of everything properly.
Now you’re at the bare steel, you washed/rinsed it with soap and water right? Thoroughly? Good. Put that thing on something that will allow it to lay flat and can get wet. (i.e. not a cardboard box) sand with 300 - 400. The metal is pretty smooth; you just want to rough it up so the primer will stick better.
Holding the can
Hold the can at a 30 to 45 angle to the piece your painting and keeping the spay pattern perpendicular as you move the can.
Start before the piece, move left to right (other way if your left handed). This is actually important. It is easier for your wrist to release tension evenly than to apply it evenly. Be prepared to take a sideways step if the piece is large or your arms are short.
Wet sanding.
Soak your paper. And use really warm water. Use a sanding bock. The weight of your had is enough pressure.
Edge painting.
Feather your edges. I will do an edge coat let it dry, and then paint as normal, doing the edges again, and then a final edging. It's a bit over kill though.
My Painting technique. Or 3 coats is not a magic number.
I do a lot of thin coats. I don’t really count them it kind of an ‘that looks right’ thing. It’s probably close to 6 or 7 on the primer; 9 or 10 on the color; and the clear coat really depends on how much abuse I think the case will get and where. I usually do extra edging on drive slots on the bezel.
Lightly wet sand (The idea is to make the paint even, not take it off) with 600 between each coat. Thoroughly wash and dry. And continue. When you get to the final coat of your color (or clear if your clear coating) use a really light sanding with 800 to knock off any dust, rinse to get any clumps off, then use a light sanding of 1000 grit, rinse to get any clumps off, then a light sanding with 1500. Wash and rinse. Get your favorite rubbing compound and go to town. If hand rubbing start with at least 2500 grit if you got a buffer or a low rpm drill with a buff pad use at least 3000. If you go to an auto supply store of auto paint store, hell even a body shop may sell it you can get this compound that is like 10,000-30,000 grit. It looks like soy sauce.
Plastic face plates.
Here 3 coats is the magic number.