What Grit Sandpaper after Priming?

Just a question, I've had to do a little bodywork to my 1939 M, took out dents, filled in cracks and scratches, some bondo, etc... all the sheetmetal parts are covered in primer now and I've been doing some wet sanding with 400 grit sandpaper to make the primed surface real smooth. Here's my question, what grit of sandpaper will I have to use on the primed surface before I paint the tractor? Or would the 400 grit suffice? Just curious and thanks to anyone who contributes.

ps. I used oven cleaner on my tractor to remove paint and grease.....that stuff worked awesome.....and $1.00 a can at dollar general....what a bargain...

Thanks,

Jared Jeffries

Color sanding is where one would normally use the higher grits, starting off at 600 and going up to the 1200-1500 grits before compounding with hand or a buffer. Of course, follow paint maker recommendations as some paints are not meant to be color sanded and polished out.

And, if you are using a laquer based spray can primer for your project and wet sanding it, you are actually going to cause rust to form under the paint, unless there is something like an epoxy or urethane primer to block the water. Lacquer primer is like a sponge to water and solvents....

So do you paint the surface after you have sanded with 1500 grit? I'm curious how much of a scratch I need to have in the primer for the paint to adhere. Thanks for the reply.

Jared Jeffries