Gather your things and get comfy. You will need:

• polymer clay pieces to be sanded
• medium sized bucket or pan for holding water
• comfortably sized sheets or sponges (sanding media)
• soapy or silky water (add detergent, bath foam, etc.)

The goal is to make all of the scratches left by the previous sandings finer and finer so they won't be visible after buffing or after a coating is applied.

Comfy? Begin.

1. sandpapers usually come in 9"x11" sheets, generally too big to hold in your hand or for sanding small objects, so cut or tear them down to size. Make sure you write the grit values on the back with a permanent marker because whatever is already printed on the back might not show on a smaller piece.
2. soak the papers until they get a little less stiff, set aside all the sanding media except the one you need at the time. start with the coarsest media.
3. toss in your polymer clay pieces into the water.
4. sand in a circular motion as much as possible, use gentle pressure. rinse the media and your piece when you notice the scraped material (debris) clogging your media. the soap helps reduce clogging.
5. after sanding each piece on all appropriate surfaces/sides, set that piece aside (outside of the pan). this will help you keep track of what needs to be sanded and what has been sanded. one way to tell if you've sanded the entire surface is to apply a acrylic paint wash to the surface and let it dry. if you don't see any paint on the surface after sanding, you've done a good job.
6. when you've finished that round, rinse your sanded pieces, empty the pan and refill with fresh soapy water. this will help prevent any coarser grits getting into the finer sanding levels.
7. repeat steps 3-6 with the next finer grit.
8. when you're done sanding, rinse your pieces well in clean water then wipe them well with a soft cloth.

Note 1: Ergonomics
It is possible to hand sand without causing damage or pain to yourself. I can't recommend any specific positions or devices, but I would recommend if you experience any pain or discomfort while sanding, take a break. Then change things around; the positions of your hands, arms, wrists, change your sanding height level. Relax your shoulders. Take your time. Take frequent breaks. You may eventually discover the magic formula of how to position yourself and amount of sanding pressure for a tolerable or even pleasant sanding experience. If you do, let folks know! ;-)

Note 2: Papers vs sponges
Papers are fine for nearly every situation. Sanding sponges for better suited for contoured surfaces because they will follow the uneven surfaces better. If you can't find sanding sponges, you can wrap a sheet of sandpaper around a regular kitchen sponge.

Note 3: Post-sanding white residue
Sometimes after sanding, the might be some white residue on your pieces after they've dried. If rinsing and wiping didn't prevent that from appearing, try rebaking for 10-15 minutes, or zap with a heat gun.

OK. Me and battery powered tools aren't the best of friends. I only use them when I have no better choice, like for a cell phone, etc. But at home, gimme A/C current. I don't have to worry about recharging and keeping track of various power pack supplies.

So I can't really address modified electric toothbrushes, stain brushes, etc. because I've not used them.

Eva (Mejsel) of Denmark has. She modified an electric toothbrush. Her efforts are highly worthy of mention. She posted the info at polymerclaycentral.com's message board in this message.

These little appliances seem ideal for sanding small objects and getting into small spaces. Since electric toothbrushes, stain brushes and the like a pretty common and inexpensive these days, it seems a nice choice.

The toothbrush, your sandpaper set, a little glue and you're good to go,

I've already done a separate tute for that specific task. Click here. I must confess, I don't use my Mouse for wet sanding unless I'm doing production level work, which I avoid these days.

Why just for production level work? Two small reasons. One, the vibrating hand held device that has a wet sanding surface can get a little messy if one doesn't have the proper setup to contain the spray. Two, the sandpaper must be velcro-ed to the Mouse. It can be hard to pull those sheets off to change them when you've got tendonitis, etc. If I had a mouse for each grit, then sweet. Otherwise, not so sweet.

I've done a separate tute for that as well. Click here for a tute on using river rocks in a tumbler to sand polymer clay. Unless I've literally only 1-2 beads, I will use my tumblers and rocks to sand.

You've a tumbler and sandpaper, but no river rocks? Click here for a tute on how I used sandpaper to tumble sand polymer clay.