[Guiddy]

I always start with body on any model, as the time spent primering and drying can be spent assembling the rest of the kit.

So to spray a solid colour I do the following...

The body has the mold lines removed with a set of needle pliers, before finishing the whole body with a rub down using 800 grade wet and dry paper. Just enough to remove any scratch marks and give the primer something to key into.
Make sure you file the mold lines off whilst having a picture of the car near by! You don't want to remove what ends up being a panel line!
Wash with soapy water and a new toothbrush (Buy it yourself and don't pinch anyone elses!!!)
Rinse and leave to air dry where it won't get dusty or bitty.

Now, purchase some acrylic based Automotive primer, plastic primer is even better.
Grey for darker colours, white if it is red, yellow or white as they are translucent and show what's beneath.
If you live in the UK watch Halfords primer as it doesn't like base coats over the top, it cracks!

Our Subaru here is going to be white, so for this Halfords acrylic primer was fine.

Give the body three coats of primer, the first one being light, and then leave to harden for 24 hours.
Check your filing was done well and that no finishing needs doing.
If so, have another go to remove any imperfections and add primer to that area 24 hours later.

Primer MUST harden for 24 hours to avoid shrinkage.