Thank you for your reply. I will not be sanding anymore. LOL

Paint doesnt always stay on my boxes, I've tried several kinds. Especially where the soil is wet, I think our soil or swamp runoff is acidic, eats through the paint.

Depends on the kind of paint. I've used some paint where it started to scratch off before I got it to the woods. I always sand mine.

Yes. I recommend getting a fine grit foam sanding block. It makes that job quick 'n easy.

It's also helpful to wash your boxes before painting, even if they're brand new. Plastic normally has a residue of a release agent that helps pop it out of the mold. Paint won't stick to that release agent, but a simple washing will get rid of it.