Step 4: Clean
After a couple of minutes of sloshing the solvent around, your seals will probably start to leak. At this point, or whenever you think you've cleaned long enough, with the unit over the bucket carefully remove whichever seal is leaking the worst and pour the used acetone into the bucket. You know it's been working because it goes in clear and comes out a sickly brown.
If the solvent you poured out was really dirty then pour a couple more splashes in and rinse it. I ended up rinsing mine 4-5 more times because it was so dirty. There is no need to re-seal the open end at this point if you are careful.