1. Open printer.
2. Remove toner cartridges.
3. Find the waste tank at the left side.
4. Remove by pulling straight out.
5. Dump out the tank. (Obviously very messy, best done in a garage.)
6. Blow out the tank with air or Dust-Off. (Obviously very messy, best done outside.)
7. Check that the clear lenses on the side of the tank seem reasonably clean. If not, blow off again.
8. Replace tank and cartridges.
Don't snort the toner.