Nativity puzzle and request for advice

[NobodysWeasel]

I grew up with a nativity puzzle in my house, which was one of the things that got me interested in puzzle making in the first place. I finally got around to scanning it and making my own pattern from it(I understand the original pattern came from a magazine in the 70's?, but I haven't been able to find it). I've included 2 pictures.

So now the request for advice. I've made 2 or 3 puzzles now that I've wanted to paint each piece on all sides. Every time I do, the pieces expand slightly, making the puzzle a very, very tight fit. I already am using the largest blade I have (forget the number at the moment), but I know there are larger ones on the market. So is the solution to just use a bigger blade? Or do I need to sand down the edges of the pieces more? Or use a different kind of paint (using acrylics right now)? Or something else entirely?

On a semi-related note, does anyone have any suggestions for power sanding equipment? I've been doing all my sanding by hand so far, and I'm new to the woodworking thing in general, so I don't really know what's appropriate for a hobbyist. And if the solution really is to sand the pieces more, this may be a necessary purchase.

Thanks for any answers you may have, and thanks for all the answers I've already found by lurking around this forum!

[DBourdon]

You could expand the size of the tray by 1/8" all around to account for the expansion in the pieces.

Or you could stain the pieces and avoid the expansion all together.

[wood-n-things]

I make a lot of children's puzzles and I never ever paint the edges where the pieces join. It is just too much of a headache. I also use acrylics to paint them when I paint them. I really dislike painting wood so I let the parents do that but I caution them about painting the adjoining faces for this very reason.