Wow dude,you really sanded off the paint from the panel.

You must be in a really great mood to sand all that.
Try smoothen all the panel 1st by using 1000 and 1200 grit.You need to do this from preventing swirl from appearing when you painted it.

Before you apply the color you want,eg: yellow,paint a proper primer for a few (2 layers) first.
After that,you can start to paint the color of your choice.

You will see the different.

All right,to make it easy.From the pictures above,you can see a swirl at the panel side.Well,if you apply some 1k to 1.2k grit,it would remove the swirl and you paint will be so smooth.

Primer is a very light color like white,silver,gray.

You're wellcome friend.
Well,brown is not a undercoat / primer.
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You only need primer / undercoat IF you plan to paint color such as (red,blue,yellow,or normal color) depends on the original color of the surface.
You MUST apply primer / undercoat IF you plan to paint color like (metallic,pearl,candy,etc)

Clear coat / transparent paint is not so recommended bro.If will just ruin you paint as it will not really gives a gloss effect.UNLESS you use a great cleat coat that is using a gun-spray paint.

Its kind of hard for you to remove the blue paint without removing the color below it.The paint already sticks to each other.
Why don't you just sand all over again and start fresh.

Thanx.
All right.Before you want to paint,you need to see the default color of the surface.As for black family,its the darkest color,so it doesn't need any primer.

No problem mate.
Normally,most of the paint will state "primer"..

The Joker?? Well,seems to be a good start and a great name.I will keep up with it.

Spraying Guide