Many of you have asked about how we make our dorodangos. You can try dorodango.com for some good links and basic information. That's where we started.
We're certainly not experts. We're each now four mudballs into the endeavour. Our efforts are still rudimentary at best. But we're improving! See the photo for a comparison of my first doro (on the left) to today's as-yet-unpolished effort. Lots smoother! So, for what it is worth, here is some of what we've discovered.
Put your dirt through a sieve. A coarse sieve is fine for the initial muck-ball formation. Your soil can be fairly sandy if that's what you've got, but get the roots and leaves out. A finer sieve, and use of soil with a higher clay content, is best for the later stages.
About the various stages. There are basically three. First you start with wet dirt and your ball will feel jiggly and mucky. Handle it plenty, encouraging it to be a round shape. You can dust it with a bit of dry dirt once or twice, but don't do more than that. Adding too much dry dirt on the surface too soon can lead to cracking. We handle our jiggly mud for 20-30 minutes, at the end of which it's still slightly glistening with wetness on the surface. It seems like nothing has happened, but lingering at this stage is fun (muck!) and it seems to prevent cracks from developing. Don't squeeze to get rid of the water -- subsequent applications of dirt will draw moisture out; squeezing will cause cracking.
During the next stage you add dustings of dirt to form a proto-capsule, which will make the dorodango quite firm by the time you are done. Use fine-screened dirt with a reasonably high clay content. Again, don't squeeze, and don't hurry. Trickle on a tiny mountain of dry dirt, and brush most of it off gently with your thumb. Rotate and repeat. Use your palm to gently smooth off the excess. Once all trace of actual wetness is gone and the shell of the ball is feeling fairly strong, get a small jar about three-quarters of the diameter of the dorodango. Place the open end of the jar against part of the dorodango and move it in small circles extremely gently to smooth the damp-but-not-moist ball. Continue over the entire surface.
If it's not totally smooth now, you can place it in a closed Ziploc bag or under a jar until the surface feels a bit moist again, then repeat a bit more of the proto-capsule step.
Now the dorodango should rest for a while. An hour in the sun outside, or a few hours inside. It will shrink and firm up, hopefully without cracking. (Our cracks have all occured within the first 20-30 minutes.)
The final capsule creation is something we haven't really mastered yet. Glossiness and strength seem to be a bit of an artisans' secret. Tips or suggestions are welcome. We've managed a sort of semi-gloss finish on a couple of ours. We can only dream of something approaching the lacquer-like finish on the ones on the dorodango.com site.