Personally, I would use MDF.
Sanding it until it feels smooth to touch, primer and sand again with a very fine paper, then spray.
If you're looking for a very smooth glossy finish, this will get you there a lot faster.
Build the box and the grid separate. That would make it easier to get painted to your liking.
Both are painted, you simply slide the grid into the box (carefully so you don't damage the nice new paint job) and you're done.
Sanding it until it feels smooth to touch, primer and sand again with a very fine paper, then spray.
If you're looking for a very smooth glossy finish, this will get you there a lot faster.
Build the box and the grid separate. That would make it easier to get painted to your liking.
Both are painted, you simply slide the grid into the box (carefully so you don't damage the nice new paint job) and you're done.
