Honestly no one can tell you which grinder will work best... "best" is subjective, although I think we can all agree here that the "best" grind is as fine as possible for this vaporizer. I liked my 2 piece Space Case while I was using it, but like I've mentioned I don't use it anymore.
I stopped using my 4 piece Sharp Stone when I realized that collecting the kief was causing me to go through more flower for the same effects... it makes sense since the herb itself was getting kief'd, most of the cannabinoid concentration was in the kief, and I was gonna vape it anyways... so I just used the 2 piece instead. Kept the kief together with the herb, and I could grind a few trenches at a time. All is well again.
Using the coffee grinder has the advantage for me of grinding ALL my herb at once and getting it over with. I've had a few serious arthritis flare-ups lately and I'm more and more grateful everyday that I already had everything ground down. All I have to do now is find my little herb vial, dump some onto the box, and I'm good. Week and a half ago it was so bad that I couldn't peel an orange, so I can't imagine what that would have been like opening my nug bottles, breaking some off, de-stemming, putting it in the grinder, twist twist twist etc. I totally understand if some people don't want to use one, grinding 4g's at a time is a "commitment" of sorts.
Anyways, going to the headshop in an hour's time. I saw some glass "sponge" screens last time I was in there some months ago (when I got my water pipe actually.) Do you guys think, I could buy one and put it in the box, and then put maybe a sliver of hash on that? When I say it's a "sponge" screen, I mean if you look at a sponge, how there's those holes throughout it? The screen is a circular disk like that. I'll see about it, but why wouldn't it work? All I see going wrong is the hash melting through the disk into the screen... :/