You’re overthinking it @dan1…
All you’ve got to do is knock them off and size select through a (series of) screen(s).
The above was suggested two weeks ago.
Have you tried it?!?
Get a microscope (even an augmented cellphone) so you can see what you’re doing…and I recommend In House analytics of some flavor (TLC?) so you can actually measure both purity and how much you’re leaving behind
…then get at it!