I have no trouble doing DCC sends on IRC.

Some of my buddies cannot however, since they are behind NAT.
According to some sources, I could do a DCC server that would allow them to connect to me in order to send their file, bypassing the fact that they are not reachable in the WAN. Likewise there seem to be other things such as reverse DCC and passive DCC. Unfortunately, there seems to be very little documentation on how to use these features. I have successfully opened a DCC server, but I have no idea what commands they should use to connect and send me their file. The other solutions are even more mysterious to me.

Any help would be greatly appreciated. We are all using irssi if that makes a difference.