You can speed up the process if you don't do any filtering in VirtualDub and instead do all the resizing and smoothing within the AVISynth script and only using VirtualDub with the Video Processing set to Fast Recompress to save the HuffYUV file. The problem is that while this approach is faster, it's not as Visual and can be harder to do properly.
That's pretty much it off the top of my head. I'd like to mention TitanTV.com though. This site is a really handy guide for DTV, and even can integrate with the HiPix card :). Make sure you ignore their antenna guide though.
For another long and boring post by yours truly, check out my post on AVSForum regarding my HDTV journey.
Another thing to mention about the encoding instructions is that with the 720p .avs method, you will lose some resolution this way. The "proper" way involves weaving and frame dropping, and each configuration must be individually tweaked. It's very tedious, and not worth it for the extra few hundred lines of res. At 720p you're already going to be kicking ass, especially when it's resized to half the res at x360 for SVCD.
Final quick note. If you get an AC3 Sync Error using HDTVtoMPEG2, then use bbdmux (also included) to demux the audio stream to .ac3. Then use azid to convert the .ac3 to .wav and mux it into the video the same as you normally would.
That's it folks.
Click "NEXT" for a list of tools used for following this tutorial.