I could be mistaken, but I seem to recall that the files themselves needed some sort of metadata set on them for them to be categorized as a podcast. Try googling around for that.
There is an "Automatically Add to iTunes" folder that Hazel could toss the mp3 in. But the problem is getting iTunes to classify the mp3 as a Podcast instead of music.
I haven't found an answer on how to automate that.
I just let a day's worth build up and manually convert them to podcasts.
Right Click on the file once it's in iTunes. Click on the 4th Tab "options". The second drop down is "Media Kind". Select "podCast". Hit "ok". Done.
From what I can tell, you can't automate it via AppleScript. Looking at the iTunes AppleScript dictionary, it shows that a track has a "podcast" flag but it's read-only so it seems that you can't set it from a script.
As mentioned in the other thread, this is a bit beyond the support I can give though maybe someone else can help you out here. A quick look at the script seems to indicate that it creates a temporary web server on your machine which it then tells iTunes to subscribe to the podcast which it is hosting. A bit convoluted but it may work.