Zoo- I get my prop down to say the size of cornmeal, by using a cheap coffee grinder, I'm not sure I can get it finer than that.
I had a hive last year that looked just like the tar image you spoke of, every time I did a hive inspection I would wait until the sun had warmed the hive real good, the prop just scrapes right off like frosting.
You will need:
A hammer
Ziplock baggies - sandwich size or quart size.
Cheap electric coffee grinder from a thrift shop or they are about $10 at Walmart.
A cereal size spoon
This is what you do:
Scrape off all the prop you can, or some people use a prop screen. Put it all in a ziplok bag or several ziploc bags. Freeze it overnight. This is where you have to work in smaller batches and work quickly because the prop starts to get room temp and gets real sticky again.
Have the hammer ready. Take one prop zippy out of the freezer, then promptly wack away at the prop in the zippy until it starts to fracture into smaller pieces, it breaks up like ice. If it starts to stick together put it back into the freezer, for about 1/2 hour. Start on another baggie. Keep doing this until the pieces are about the size of a piece of rice. Freeze it again. Always work with it Frozen!
Then put about 1/4 of a cup of the rice size prop into the coffee grinder, and pulse it often scraping the sides often. You may need to detach the coffee bean canister that's holding the prop and put it back into the freezer for a little while.
Now! Once you've got the prop pulsed down the the size of cornmeal, put it into zippy's and keep it frozen until your ready to use it for a project.
I haven't tried to put this cornmeal size into a cup of coffee or tea, but you got my curiosity up so I'll have to see if it dissolves in my coffee tomorrow.
Have fun!