Pollination is fairly simple when dealing with such large platns as C. cordata, just stuck a paintbrush inside the tube and moved it around a little bit, this I did with two plants, the result was this fruit, and one other on the other plant, that died because i had to move the plants to their new home.
I think that for the smaller Crypt species you should probably be more gentle, taking a very thin stick, coating it with cotton will do just fine.
If you have the possibility to do this, then do it, as it is rather exciting to see the fruit develop, and perhaps you can even get you some seeds if you are in luck
