I think i've finally gotten good at inserting(c-fold works best for me) and getting it to pop open.
on an amusing note, one day i left it in a bit too long, and when i took it out, it had a sour milk smell to it. so i rinsed and rinsed and quick-soaked it, and then added a couple drops of sweet orange essential oil to some hot water. rinsed it clean, soaped and rinsed one last time, re-inserted. fast forward to last night, took out my nearly empty cup to clean before i put it away again. set it on my bookshelf to dry.
come back in my room later.
and say "why does it smell like oranges in here...?"
heh, at least it got rid of the bad smell.