For some reason Virtual Dubs tends to crash during rendering and I can't really do something about it. I tried Avidemux before but the audio insertion didn't work, so I dropped it (video however worked totally fine). Now, after exporting and adjusting the recorded commentary with Audacity, the encoding changed and suddenly Avidemux was able to read it! If that's not nice - now I just need to find some good codec to store the videos lossless and then mix in my commentary. Awesome, after Virtual Dub's repeated fail I thought that I'd have to buy a commercial video editor and lost faith in open source alternatives.
I can't repeat how much I dislike the whole multimedia editing software stuff. I mean it's not that it isn't the same for graphics and IDEs, but video editing is the most annoying thing ever. Anyway, I hope Avidemux' results are good enough for my needs. I don't mind storing Gigabytes of videos but I want to upload as short as possible - having good compression is necessary.