I haven't encountered that problem yet... looks pretty caked up. Mmmmm. I can't say for sure that this will "clean" your grinder, but I have found that when dealing with delicate particles, a paintbrush works amazing. I read a post on here talking about using a paint brush to handle your pollen, so I went out and bought one of those cheapo watercolor paintbrush sets (6 brushes included) for like $2 usd. The finest point one works great for getting in the nooks and crannies, and then there is a harder, flat tipped (still small) brush that works great to round up pollen. If you were to use that harder brush, you could just keep working it until most of it went through... or at least loosened it up, that way it won't damage your screen. It is obviously going to push through some plant matter, so it is not a great way to keep the pollen seperate.. but should work to clear it up a bit.
But my tip of the month... When handling pollen/kif a small paintbrush works so well I cringe at the days of using a business card, watching the edge of it turn a bright green... knowing I was losing valuables. Or even worse, the days when I used my fingers..... ahh... if I only knew then what I know now. Hahaha. Good luck, looks like you got your work cut out for you.
:thumbsup: