By hand it will get done but you'll have stumps for fingers and the rest of your life polishing.
A mouse sander is only good for the flat areas. You'll never get into the tight. Areas and there's a risk of sanding down the contours too far.
Ok here's what you need.
A drill
Flap wheels 3 sizes from 1/2", 1" and 2". Grit levels needed 120, 240, 360.
Wet and dry paper 120, 240, 360, 500 and so on.
If you have access to a bench polisher get hold of 2 pop sizes 2" and 6 or 8". In each size you'll need a Sisal, Stitched mop and loose mop.
Keep at it and trust me you'll feel defeated for 80% of the process. My first plenum took 30hrs only because I had to learn the process. You'll find out the hard way the issues as you race forward to get it done. I've dealt with a couple of half hearted attempts supplied to me to fix and its all about the prep. If you don't prep the surface correctly you'll rise through grit levels and leave marks in the finish.
My plenums leave in top quality mirror finish, if it meets my own standards then I release it. If not I go back a couple of stages with the mops and spend more time getting it perfect.
Only another minimum 18.5hrs to go. Maybe this will spur you on a bit......
And here you can see the benefits of using a bench polisher. Which on the left is upto 500 grit and the right side is the full range of mops from cut, cut/finish, finish.
Keep at it